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Biomedical subjects

G Li

Publications and source records attributed to G Li.

At least 631 records · Page 35Linked to original sources
PubMed1997

A note on sample size determination for bioequivalence studies with high-order crossover designs.

Similar to Liu and Chow, approximate formulas for sample size determination are derived based on Schuirmann's two one-sided tests procedure for bioequivalence studies for the additive and the multiplicative models under various higher order crossover designs for comparing two formulations of a drug product. The higher order crossover designs under study include Balaam's design, the two-sequence dual design, and two four-period designs (with two and four sequences), which are commonly used for assessment of bioequivalence between formulations. The derived formulas are simple enough to be carried out with a pocket calculator. The number of subjects required for each of the four higher order designs are tabulated for selected powers and various parameter values.

Clinical Trials as Topic↗
PubMed1997

Injury patterns in aviation-related fatalities. Implications for preventive strategies.

Autopsy data from individual aviation crashes have long been used in aviation safety research in the form of case reports and case series studies. Injuries sustained from aviation crashes, however, have not been well documented at a national level. This study examines the injury patterns for persons who died in aviation crashes in the United States and the implications for preventive strategies. Death certificate data for all aviation-related fatalities for the years 1980 (n = 1,543) and 1990 (n = 1.011) were obtained from the National Center for Health Statistics. The immediate cause of death and all injury diagnoses recorded on the death certificates were analyzed in relation to year of injury, crash category, and type of victim. Despite a 34% reduction in the number of aviation-related fatalities between 1980 and 1990, injury patterns were fairly stable. Multiple injuries were listed as the immediate cause of death in 42% of the fatalities, followed by head injury (22%); internal injury of thorax, abdomen, or pelvis (12%); burns (4%); and drowning (3%). Head injuries were most common among children. The majority (86%) died at the scene or were dead on arrival at the hospital. Eighteen percent of the victims were reported to have sustained a single injury, with head injury being the cause of death in nearly a third of these fatalities. Blunt injuries resulting from deceleration forces, in particular head injury, are still the most important hazard threatening occupants' survival in aviation crashes. To further reduce aviation-related fatalities requires more effective restraint systems and other improvements in aircraft design.

Accidents, Aviation↗
PubMed1997

Alcohol and injury severity: reappraisal of the continuing controversy.

It is well recognized that alcohol increases the risk of injury. It is controversial, however, whether alcohol also has an effect on the degree and outcome of injury after controlling for the severity of impact. This review examines the evidence from experimental studies in animals regarding the potentiating effects of alcohol on trauma, and the methodologic issues that may have contributed to the contradictory findings of clinical and epidemiologic studies. Most experimental studies indicate that alcohol can adversely affect the degree and outcome of injury. In controlled laboratory conditions, alcohol is found to reduce cardiac output, to increase the susceptibility to hemorrhagic shock, and to increase the pulmonary vascular resistance after standardized experimental injuries. However, it is difficult to extrapolate these findings to humans, partly because the interactive effects of chronic and acute alcohol use on trauma are rarely considered in experimental studies. The conflicting results in studies involving trauma patients are due in part to the differences in study design, particularly selection of study populations, and in measuring and controlling for kinetic forces on the body. Studies indicating that alcohol is associated with an increased risk of serious or fatal injury are usually based on data from emergency departments or police departments. The alcohol-injury severity relationship reported in these studies is attributable to a great extent to the effects of correlates of alcohol, such as speeding and not wearing seat belts, rather than the biological effects of alcohol. Studies indicating that alcohol is not associated with the degree and outcomes of injury are mostly those involving patients who were admitted to hospitals or trauma centers. Methodologic issues concerning the alcohol-injury severity controversy, including conceptual models and future research needs, are discussed.

Alcohol Drinking↗
PubMed1997

Major histocompatibility complex class II alleles in Kazak and Han populations in the Silk Route of northwestern China.

Genetic polymorphism of the HLA class II loci including the DRB1, DQA1, DQB1 and DPB1 genes was investigated by the polymerase chain reaction-restriction fragment-length polymorphism (PCR-RFLP) method in a Kazak population inhabiting the most northwestern part of China, Urümqi in the Xinjiang Uygur Zizhiqu as well as in a Han population in the same area. Forty-two Kazak and 59 Han unrelated volunteers were enrolled in this study. Among 51 DRB1 alleles tested, 29 alleles were detected, and DRB1*0301 (13.1%) and DRB1*07 (10.7%) in Kazak and DRB1*0901 (11.9%), DRB1*1501 (11.0%) and DRB1*07 (11.0%) in northwestern Han were highly predominant. In 8 DQA1 alleles detected, DQA1*0501 (29.8%) and DQA1*0301 (23.8%) in Kazak, and DQA1*0301 (28.8%) and DQA1*0102 (19.5%) in northwestern Han were the most and the second most common alleles, respectively. Of 18 DQB1 alleles tested, 14 were observed, among which DQB1*0201 and DQB1*0301 were very frequent both in Kazak (23.8% and 21.4%, respectively) and northwestern Han (18.6% and 16.9%, respectively) populations. Of 37 DPB1 alleles tested, 14 were detected. Among them, the frequencies of DPB1*0401 (21.4%), DPB1*0501 (20.2%), DPB1*0402 (19.0%) and DPB1*0201 (16.7%) in Kazak, and those of DPB1*0501 (38.1%) and DPB1*0201 (16.1%) in northwestern Han were highly increased. Several three-locus haplotypes were recognized to predominate significantly, namely DRB1*0301-DQA1*0501-DQB1*0201 (13.1%) and DRB1*0701-DQA1*0201-DQB1*0201 (8.3%) in Kazak; and DRB1*0901-DQA1*0301-DQB1*0303 (11.9%) and DRB1*0701-DQA1*0201-DQB1*0201 (10.2%) in northwestern Han. The dendrogram constructed by the neighbor-joining (NJ) method based on the allele frequencies of the DRB1, DQA1, DQB1 and DPB1 genes of 12 representative populations all over the world including northern Han, southern Han, Manchu and Japanese suggested that Kazak and northwestern Han were the closest to each other, but Kazak was a little farther from the Asian ethnic groups than northwestern Han.

Alleles↗
PubMed1997

The pathogenesis of large cell transformation in cutaneous T-cell lymphoma is not associated with t(2;5)(p23;q35) chromosomal translocation.

In 20%-50% of the advanced cutaneous T-cell lymphomas (CTCL), malignant T cells undergo large cell transformation (LCT). The malignant T cells of LCT in CTCL can share morphologic and immunophenotypic similarities with CD30 (Ki-1)-positive anaplastic large cell lymphoma (ALCL), suggesting a common mechanism of pathogenesis. The t(2;5) (p23;q35) translocation, resulting in the fusion of the nucleophosmin (NPM) gene and the anaplastic lymphoma kinase (ALK) gene, is associated with primary CD30+ ALCL. To determine whether acquisition of this chromosomal translocation is involved in the pathogenesis of LCT in CTCL, we examined 12 tumor samples from 9 CTCL patients, including 8 with LCT-CTCL and one with concurrent CTCL and Hodgkin's disease, for the presence of the t(2;5) translocation. Numerous CD30+ large cells were present in 4 LCT-CTCL consistent with secondary CD30+ ALCL; CD30 was expressed by <10% of the large cells in another case and was negative in the other 3 lymphomas. Using primers spanning the NPM/ALK fusion junction, PCR amplification following reverse transcription (RT) of mRNA failed to show the products of NPM/ALK fusion in all samples tested. Thus, the t(2;5) (p23;q35) translocation does not appear to be involved in the molecular pathogenesis of LCT in CTCL, including CD30+ cases.

Cell Transformation, Neoplastic↗
PubMed1997

Photogeneration of fluoride by the fluoroquinolone antimicrobial agents lomefloxacin and fleroxacin.

The photolysis (> 320 nm) of the fluoroquinolone antibacterial agents lomefloxacin and fleroxacin results in the loss of their F3 atoms as fluoride. The quantum yield for lomefloxacin was 0.98 at pH 7.4. The mechanism probably involves aryl-F heterolysis from the S1 state with the concomitant generation of a carbene at C-8. In contrast, the monofluorinated fluoroquinolones norfloxacin and ciprofloxacin do not generate fluoride upon irradiation. Carbenes are highly reactive species that undergo addition, insertion and abstraction reactions and can cause DNA cleavage. These findings may explain why lomefloxacin and fleroxacin are more photomutagenic and photocarcinogenic than fluoroquinolones in which C-8 is either unsubstituted or bears a substituent other than fluorine.

Anti-Infective Agents↗
PubMed1997

Characteristics and outcomes of self inflicted pediatric injuries: the role of method of suicide attempt.

OBJECTIVE: To examine the epidemiologic characteristics and clinical outcomes of self inflicted pediatric injuries in relation to the method of suicide attempt. METHODS: Using data from the National Pediatric Trauma Registry Phase II, a comparative analysis was conducted for children under 15 years of age who were admitted from 1 October 1988 through 30 April 1996 because of self inflicted injury by firearm (n = 28), hanging (n = 38), or jumping from heights (n = 21). RESULTS: Of the 87 cases under study, 90% occurred at home, and 86% occurred between noon and midnight, with a peak in early evening (between 6 pm and 7 pm)-More than one quarter (29%) had preexisting mental disorders, such as disturbance of conduct and depression. Toxicological tests were conducted on admission on 40 (46%) of the patients; 20% tested positive for alcohol or other illicit drugs. The method of suicide attempt was associated with gender and age of the patients: 75% of the firearm cases and 82% of the hanging cases were boys compared with 29% of the jumping cases (p < 0.01); 79% of the hanging cases were aged 13 years or younger compared with 39% of the firearm cases and 48% of the jumping cases (p < 0.01). The mean injury severity score was 18.6 for the firearm cases and 16.3 for the hanging cases, significantly greater than 8.5 for the jumping cases (p < 0.02). Reflecting the differences in injury severity, firearm cases and hanging cases were more likely than jumping cases to be sent to intensive care units or operating rooms from emergency departments, and to develop complications during hospitalization. The case fatality rate was 50% for the firearm cases, 32% for the hanging cases, and 5% for the jumping cases (p < 0.01). On average, these patients stayed in hospitals for 11 days and 52% of those who were alive at discharge had at least one impairment in communication, cognition, or self care functions. CONCLUSION: Boys and older children tend to use more lethal methods in suicide attempts. Even in this age group, suicide attempts often involve psychiatric disorders and acute abuse of alcohol or other illicit drugs. Firearms are associated with significantly increased risk of inhospital fatality. The clinical outcomes of self inflicted injuries appear to be worse than other injuries treated in the same trauma centers.

Adolescent↗
PubMed1997

Activation of diacylglycerol in cultured endothelial cells exposed to cyclic strain.

Confluent bovine aortic endothelial cells (EC) were grown on flexible membranes and subjected to 10% average strain at 60 cycles/min for up to 500 s. A biphasic increase in diacylglycerol (DAG) occurred, with an initial transient peak at 10 s followed by sustained elevation to 500 s. The early peak corresponded to the transient formation of inositol 1,4,5-trisphosphate, demonstrating hydrolysis of L-alpha-phosphatidylinositol (PI) by PI-specific phospholipase C. To determine the origin of the sustained DAG phase, we incubated confluent bovine aortic EC with 1 microCi/ml [14C]myristate overnight and subjected them to cyclic strain. There was a decrease in phosphatidylcholine (PC) and a corresponding increase in DAG at 10 s and 250 s, suggesting PC hydrolysis with the generation of DAG at both an early (10 s) and a late (250 s) phase. [14C]phosphatidylethanol, a specific product of phospholipase D (PLD) in the presence of 1% ethanol, was measured in EC preincubated with [14C]myristate. Cyclic strain led to an immediate and sustained activation of PLD. Increased ethanol concentration led to a consistent decrease in DAG. Furthermore, when EC were pretreated with 1% ethanol, the strain-induced proliferative response was attenuated.

Animals↗
PubMed1997

Measurement and modeling of glucose-6-phosphatase in pancreatic islets.

In the beta-cells of the pancreas, glucose phosphorylation carried out by glucokinase is the rate-controlling step in glycolysis, and the kinetic characteristics of glucokinase govern to a high degree the dose-response relationship between glucose and insulin release. Because glucose-6-phosphatase (G-6-Pase) opposes the action of glucokinase, it may have a regulatory role in the release of insulin in response to glucose if the enzyme is present in the beta-cells. A number of researchers have reported finding high levels of G-6-Pase in islets, but quantitation of its activity remains controversial, mainly because of difficulties in solubilizing a particulate enzyme. Therefore a method developed to measure functional glucose phosphorylation activity in intact brain was applied (Chi, M. M.-Y., M. E. Pusateri, J. G. Carter, B. J. Norris, D. B. McDougal, Jr., and O. H. Lowry. Anal. Biochem. 161: 508-513, 1987), and the rates of accumulation and disappearance of 2-deoxyglucose 6-phosphate (DG-6-P) in freshly harvested islets were determined as a measure of glucose cycling. Islets were incubated in the presence of 30 mM 2-deoxyglucose (DG) for 60 min, and subsequently the incubation medium was replaced with medium containing no DG, but instead high levels of mannoheptulose as a blocker of phosphorylation. The content of DG-6-P in the islets was measured at strategic times during the protocol. As predicted by a mathematical model, DG-6-P accumulated in the presence of DG and decayed after its washout. Both of these results are consistent with islets containing dephosphorylation activity for this substrate. The kinetic curves were fit using a mathematical model, and the maximal G-6-Pase activity was estimated to be 0.13 +/- 0.005 micromol x g(-1) x min(-1). However, when the physiological effect of this amount of G-6-Pase activity was assessed by use of a model of glycolysis, it was found that the impact on glucose cycling and usage was insignificant. It was concluded that normal islets do contain measurable activity for dephosphorylating glucose 6-phosphate but that this enzymatic reaction does not play a role in glucose metabolism and sensing by the normal beta-cell.

Animals↗
PubMed1997

Catalase-overexpressing transgenic mouse heart is resistant to ischemia-reperfusion injury.

Myocardial ischemia-reperfusion injury is at least partially mediated by oxygen-derived free radicals. Catalase is a major enzyme involved in the detoxification of hydrogen peroxide. The activity of catalase in the heart is very low, which may be a factor responsible for the high sensitivity of the heart to ischemia-reperfusion injury. The present study was undertaken to determine whether elevation of catalase specifically in the heart of transgenic mice can provide protection against ischemia-reperfusion injury. Hearts isolated from transgenic mice in which catalase in the heart was elevated approximately 60-fold higher than that in nontransgenic heart and from the non-transgenic littermates were subjected to 50 min of warm (37 degrees C) zero-flow ischemia followed by 90 min reflow. Compared with nontransgenic controls, transgenic hearts showed significantly improved recovery of contractile force (75 vs. 25% at the end of 90 min reperfusion, P < 0.01). Efflux of creatine kinase was reduced by approximately 50%, and the zone of myocardial infarction as demarcated by triphenyltetrazolium at the end of reperfusion was reduced by approximately 40% in transgenic hearts compared with nontransgenic controls. These findings support the view that hydrogen peroxide is an important cause of ischemia-reperfusion damage and suggest that protection may be provided by elevation of catalase activity.

Animals↗
PubMed1997

Infiltration of eosinophils into the asthmatic airways caused by interleukin 5.

Interleukin (IL)-5 is thought to play an important role in asthmatic bronchial mucosal inflammation and is a potential therapeutic target. To investigate the effect of IL-5 on the infiltration of eosinophils in airway in vivo, we compared eosinophil counts and their activation status in airways without and after the topical instillation of recombinant human IL-5. Eight subjects with mild atopic asthma underwent initial bronchoscopy during which control bronchoalveolar lavage (BAL) fluid as well as bronchial mucosa were obtained, and at the same time, normal saline and IL-5 were administered to two sublobar segments separately. The second bronchoscopy were carried out and samples from challenged sites were taken 24 h later. It was found that the total eosinophils (BMK-13+ cells) and the activated eosinophils (EG2+ cells) in bronchial mucosa, the eosinophil numbers in BAL fluid, as well as eosinophil cationic protein (ECP) in BAL fluid from saline-challenged segments were not different from those in unchallenged segments. However, a significant eosinophilia was observed in bronchial mucosa and BAL fluid from IL-5-challenged sites. Eosinophil activation, as assessed by secretion of ECP, was also increased significantly in bronchial mucosa and BAL fluid. The results strongly suggested that IL-5 is capable of inducing eosinophil infiltration into the asthmatic airways, as well as the activation of infiltrating eosinophils.

Adult↗
PubMed1997

Injuries to bicyclists in Wuhan, People's Republic of China.

OBJECTIVES: This study examined the morbidity and mortality from bicycling injuries in Wuhan, China. METHODS: Police department data for the year 1993 complemented by data from emergency room interviews were analyzed. RESULTS: The death rate from bicycling injuries was estimated as 2.2 per 100000 population, more than seven times the rate for the United States. At least 79% of the fatalities and 17% of the emergency room cases sustained head injuries, the majority (71%) of which resulted from contact of the head with the concrete or asphalt road. None of the patients was wearing a helmet at the time of injury, and helmet use among the general bicyclist population was nonexistent. CONCLUSIONS: Bicycle-related head injury is an important public health issue in China. The effectiveness of safety helmets in developing countries needs to be evaluated.

Accidents, Traffic↗
PubMed1997

Activins and activin receptors in cell growth.

Activin and inhibin, members of transforming growth factor-beta (TGFbeta) superfamily, have diverse and widespread effects within living organisms at many stages during growth and development. From the initial isolation of these growth factors based on their effects of FSH secretion, the study of these factors, as well as of the activin-binding protein follistatin, has progressed from the localization of the expression of the inhibin alpha subunit, activin betaA and betaB subunits, and activin receptors in the tissues of various organisms to the examination of activin and inhibin as autocrine and paracrine agents in cell proliferation and differentiation. The inhibitory effects on cell growth and differentiation that have been observed upon treatment of cells with activin suggest that further understanding of the bioactivity of this molecule and its characterization on a molecular level may aid in a more complete understanding of cell growth and differentiation. This minireview discusses the roles of activin, inhibin, and follistatin in the arenas of cell proliferation, differentiation, and embryogenesis, as well as the roles of these molecules in cancerous cells.

Activin Receptors↗
PubMed1997

[Expression of CerbB-2 and EGFR mRNA in human nasopharyngeal carcinomas and pericarcinomatous tissues].

Using the digoxin labelled probes and DNA-RNA in-situ hybridization technique, the expression of C-erbB-2 and EGFR mRNA in routine paraffin sections of 30 human nasopharyngeal carcinomas (NPC), 20 pericarcinomatous tissues (PCT) and 16 chronic inflammatory mucosae. The results showed the positive rates of C-erbB-2 and EGFR mRNA expression were 86.7%, 83.3% respectively in NPC and 80.0%, 70.0% in PCT, while those in chronic inflammatory mucosae were no detected. Co-expression of these two genes occurred in 83.3% of NPC and 70.0% of PCT. In the PCT, the positive rates of C-erbB-2 and EGFR mRNA in the atypic hyperplasia were higher than that in the simple hyperplasia, the amount of the positive cells of these two genes increased steadily in the mild, moderate and severe dysplasia and diffused from basal lamina of epithelium to the whole epithelium. The results suggest that the activation of C-erbB-2 and EGFR genes is an early event and play a synergic role in the carcinogenesis of NPC and examination of their expression is helpful in early diagnosis.

Carcinoma↗
PubMed1997

[Study of the mechanism of regression of left ventricular hypertrophy in hypertension treated with slow-release verapamil].

Thirty-three hypertensive patients with left ventricular hypertrophy were treated with slow-release verapamil for 1 year. The left ventricula mass index (LVMI) and the concentration of intracellular calcium ion ([Ca2+]i) of lymphocytes were studied respectively at the beginning, the third, the sixth and the twelveth month of treatment. The results revealed that: 1 the LVMI was positively correlated with [Ca2+]i and mean arterial pressure (MAP); 2 the LVMI, [Ca2+]i and MAP were significantly decreased, after treatment; 3 the degree of reduction of LVMI (delta LVMI) was positively correlated with the degree of lowering of [Ca2+]i (delta [Ca2+]i) and MAP (delta MAP); 4 the LVMI and [Ca2+]i showed no significant change at the third month but significant decrease at the sixth and twelveth month of treatment. It suggests that besides the decrease of MAP the decrease of [Ca2+]i is a significant factor for mechanism of regression of LVH.

Adult↗
PubMed1997

[The role of opioid receptors of arcuate nucleus in cytokine-induced hyperthermia].

The present study is to define the role played by the opioid receptors of ARH in the regulation of body temperature. 1 microliter of IL-1 beta (as pyrogen) was injected into the ARH of male Sprague-Dawley rat with an automatic micromanipulator to induce hyperthermia. 30 minutes prior to the injection of pyrogen, the experimental groups were pre-treated with general opioid receptor antagonist naloxone (Nal), selective mu, delta, kappa receptor antagonists CTAP, NTI, nor-BNI respectively. Controls were pre-treated with saline. The results showed that IL-1 beta-induced hyperthermia was blocked by Nal and CTAP, suggesting the involvement of, or mediation by, ARH opioid receptors (mainly the mu type) in IL-1 beta-induced hyperthermia. The blockade by delta and kappa antagonists was not remarkable. Thus their participation in this process is less likely. The similarity between the roles of opioid receptors of ARH and POAH in IL-1 beta-induced hyperthermia strongly supports the view that ARH may be an important component of the thermoregulatory center.

Animals↗
PubMed1997

[Determination of fluoroacetatamide and fluoroacetic acid by capillary gas chromatography].

A rapid qualitative and quantitative analysis of fluoroacetatamide and fluoroacetic acid in rodenticides by capillary gaschromatography was described in this paper. Isoamyl alcohol was used as the internal standard. The determination curves of fluoroacetatamide and fluoroacetic acid in rodenticides were linear in the ranges of 0.0625-4 mg/ml and 0.625-20 mg/ml. The detection limits of fluoroacetatamide and fluoroacetic acid were 31.25 micrograms/ml (32.5 ng) and 625 micrograms/ml (625 ng), 87.5% and 30% of rodenticides sold in Taiyuan ground market from May, 1995 to May, 1996 contain fluoroacetatamide and fluoroacetic acid.

Chromatography, Gas↗