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Biomedical subjects

J Shen

Publications and source records attributed to J Shen.

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

Scavenging effect of Chinonin on NO and oxygen free radicals and its protective effect on the myocardium from the injury of ischemia-reperfusion.

The scavenging effect of Chinonin on NO and oxygen free radicals and its protective effect on myocardium from the ischemia-reperfusion injury was studied with electron spin resonance (ESR) and chemiluminescence techniques. Chinonin can effectively inhibit the oxidative activity of ONOO-, (the IC50 = 7 x 10 (-5) mmol/L) and scavenge oxygen free radicals generated from the reaction of xanthine and xanthine oxidase (the IC50 = 2/5 x 10(-4) mmol/l). It is difficult to find another antioxidant which can scavenge so effectively both ONOO- and oxygen free radicals simultaneously. In the system of ischemia-reperfusion injury of myocardium, Chinonin can, in parallel, scavenge the NO and oxygen free radicals generated from the ischemia-reperfused myocardium, and decrease the activities of lactate dehydrogenase (LDH) and creatine kinase (CK) in the coronary artery effluent of ischemia-reperfused heart and therefore protect the heart from ischemia-reperfusion injury. The protective effect of 0.1 mmol/l Chinonin is similar to that of 1500 U/ml SOD and catalase.

Animals↗
PubMed1996

Comparisons for body mass index and body fat percent among Puerto Ricans, blacks, whites and Asians living in the New York City area.

The latest data (NHANES III) from the National Center for Health Statistics (NCHS) show that the black population has the highest proportion of overweight among all adult populations in the United States. The present study compared the body mass index (BMI) and body fat percent from dual-photon absorptiometry in 1,324 healthy adults aged 18 to 107 years recruited from four ethnic groups in the New York City area; 523 whites, 280 blacks, 267 Asians and 254 Puerto Ricans. Puerto Ricans had the largest BMI and the largest percent of subjects with body weight more than 120% of their ideal weight, and the largest fat percent of the four ethnic groups: 76% of Puerto Rican males had fat percent above the median value for white males (fat percent = 19.6%) and 95% of Puerto Rican females had fat percent above the median for white females (fat percent = 30.8%). Asians had the smallest BMI, but 63% of them had fat percent above the median values for whites in each gender. Puerto Ricans also had the largest waist-to-hip ratios among the four ethnic groups. In blacks, the percent of subjects with fat percent larger than the median for whites was slightly smaller than that for Puerto Ricans, 64% and 82% of males and females respectively. These results differ from the latest NCHS data and show that Puerto Ricans in this sample are heavier and fatter than blacks.

Adipose Tissue↗
PubMed1996

Effects of ofloxacin on the pharmacokinetics and pharmacodynamics of procainamide.

Procainamide is a class I antiarrhythmic agent that undergoes active tubular secretion through the organic cation transport system, with approximately 50% of a dose excreted in the urine as unchanged drug. The remainder is metabolized to an active metabolite, n-acetyl procainamide (NAPA). Ofloxacin is a fluoroquinolone antibiotic that is excreted in the urine as unchanged drug via active tubular secretion and glomerular filtration. To test the hypothesis that ofloxacin may interfere with the renal elimination of procainamide, 9 healthy volunteers were randomly assigned to receive 1 g of oral procainamide as a single dose with or without pretreatment with 400 mg of ofloxacin twice a day for 5 doses. Blood and urine samples were obtained and pharmacokinetic parameters for procainamide were determined for each treatment period. Standard 12-lead and signal-averaged electrocardiographic recordings were used for pharmacodynamic analysis. The mean area under the concentration-time curve (AUC) and peak plasma concentration (Cmax; mug/mL) for procainamide increased by 27% and 21%, respectively, and the plasma clearance for procainamide decreased by an average of 22% with coadministration of ofloxacin. Ofloxacin did not significantly influence the pharmacokinetics of NAPA, nor were pharmacodynamics of procainamide significantly affected by coadministration of ofloxacin. These results suggest that procainamide concentrations should be monitored closely when coadministered with ofloxacin.

Administration, Oral↗
PubMed1996

Use of amplitude and frequency transformations to generate adiabatic pulses of wide bandwidth and low RF power deposition.

An amplitude transformation of adiabatic pulses stated previously [Baum et al., Phys. Rev. A 32, 3435-3447 (1985)] is generalized using the Bloch equations. Both amplitude and frequency transformations are used to create new adiabatic pulses of wide bandwidth and low RF power deposition. Several adiabatic pulses (including the tanh/tan pulse used for construction of BIR-4, SSAP, and BISEP pulses) are transformed into new pulses. These new pulses are demonstrated numerically and experimentally to operate at a significantly lower RF power level while maintaining the same performance or over a wider bandwidth while using the same RF power. They are expected to be useful for in vivo NMR experiments, especially for applications involving wide frequency dispersion and pulse sequences composed of many adiabatic half-passage pulses.

Magnetic Resonance Imaging↗
PubMed1996

A comparison of early (E7) and late (L1) primer-mediated amplification of papillomaviral DNA in cervical neoplasia.

Studies have demonstrated that in 50-90% of cervical carcinomas, human papillomavirus (HPV) DNA sequences are covalently bound (integrated) to the chromosomal DNA. All evidence shows that when integration takes place disruption of the viral genome occurs downstream to the E7 open reading frame, which is invariably retained in functional form. Theoretically, this phenomenon could result in loss of HPV sequences (L1) not critical to the presumed tumourigenic functions and if so, could influence primer selection for HPV DNA detection in these tumours. A series of cervical carcinomas (CA, n = 133), adenocarcinomas in situ (ACIS, n = 28) and high grade squamous intraepithelial lesions (HSIL, n = 30) were analysed for HPV nucleic acids using primers designed to amplify the E7 and L1 regions. Primer sizes and sensitivities were adjusted to produce equivalent amplification efficiency. Of 191 cases studied, 134 (70%) scored positive for HPV16 or 18 with either the E7 or L1 primer set. Of these, 116 (87%) were positive with both primer pairs. There were no significant differences in proportions of HPV 16/18 positives or lesion types scoring positive exclusively with the E7 vs the L1 primer sets. However, HPV18 associated, E7 positive carcinomas were slightly less likely than HPV16 associated carcinomas to be L1 positive (P = 0.07). Although a high proportion of HPV16 and particularly HPV18 positive carcinomas have been associated with exclusively integrated HPV DNA, there is little evidence that this influences detection sensitivity with E7 vs L1 primers. The combination of E7 and L1 primers provided the maximum sensitivity in this study, with 18 of 134 cases scoring positive with only one primer set.

Carcinoma↗
PubMed1996

Tumor angiogenesis in pheochromocytomas and paragangliomas.

BACKGROUND: Angiogenesis correlates with growth and likely metastases in several tumors. To determine whether it has a similar role in pheochromocytomas, immunohistochemical staining of factor VIII was done on the tumor tissue of 42 patients. METHODS: Formalin-fixed, paraffin-embedded tissue was obtained from 29 women and 13 men with 24 primary adrenal and 18 extraadrenal pheochromocytomas. Patients were divided into two groups. Group 1 included 32 patients with benign pheochromocytomas, and group 2 included 10 patients with malignant tumors evidenced by capsular or vascular invasion (six), liver metastases (three), or periaortic lymph node metastases (one). Blood vessels highlighted by factor VIII staining of endothelial cells with labeled streptavidin-biotin were counted under light microscopy. Mean vessel count within a 10 mm2 micrometer disk was calculated under x100, x200, and x400 magnification fields. RESULTS: There were no significant differences in patient age or clinical symptoms between the groups. The mean tumor size in group 2 of 8.8 +/- 5.3 cm was larger than the mean of 4.8 +/- 2.8 cm in group 1 (p < 0.005). The mean counts of vessels in the x100, x200, and x400 magnification fields were 102 +/- 48, 40 +/- 18, and 19 +/- 9 in group 1, and 203 +/- 77, 73 +/- 28, and 37 +/- 15 in group 2. The number of blood vessels in group 2 was significantly higher than in group 1 (p < 0.001) in each studied field. CONCLUSIONS: In this study the number of tumor blood vessels correlated with the invasive behavior of pheochromocytomas. Tumor angiogenesis may be useful in determining the likelihood of malignant behavior in pheochromocytomas.

Adolescent↗
PubMed1996

Dielectric analysis of phosphorylcholine head group mobility in egg lecithin liposomes.

PURPOSE: A knowledge of the interfacial properties of lecithin underpins our understanding of many of the physicochemical characteristics of drug delivery systems such as liposomes and lecithin stabilized microemulsions. In order to further this understanding, a high frequency dielectric study of the interfacial properties of egg lecithin liposomes was undertaken. METHODS: The effect of temperature, lecithin concentration and probe sonication on the interfacial dielectric properties of liposomal suspensions was investigated by high frequency dielectric relaxation spectroscopy between 0.2-6 GHz. RESULTS: The frequency dependent permittivity of each suspension exhibited a dielectric dispersion centred around 100 MHz, corresponding to the relaxation of zwitterionic head groups. The activation energy for head group reorientation was estimated as delta H = 6.3 kJ mol-1. There was an increase in extent of inter-head group interactions on increasing the liposome volume fraction, whereas the effect of probe sonication showed that: (i) head groups in both the outer and inner lamellae contribute to the dielectric response; (ii) the head groups may be less restricted in liposomes of high surface curvature with few lamellae; (iii) the high frequency permittivity of the suspension increased on sonication, as a result of a reduction in the amount of (depolarized) interlamellar water following a reduction in the number of lamellae per liposome. CONCLUSIONS: Dielectric analysis of the zwitterionic head groups of lecithin therefore provides a means for investigating the surface of lecithin liposomes, and may be used to investigate the effect of drugs and other solutes on membranes.

Eggs↗
PubMed1996

Differential effects of selective immunotoxic lesions of medial septal cholinergic cells on spatial working and reference memory.

The effect of injection into the medial septum of a toxin selective for cholinergic neurons, 192 IgG-saporin, was examined in rats trained to perform 2 versions of the radial 8-arm maze task. Rats were first trained to perform a task with varying delays (0, 1, 2 min) imposed between the 4th correct arm choice and access to all 8 arms. Lesioned rats made significantly more errors in the first 4 choices compared with controls and significantly more errors after delays; however, this effect was not delay dependent. Rats were then trained on a different version of this 8-arm maze task in which they learned to avoid 2 arms that were never baited. There was no treatment effect on acquisition of this task. These data are consistent with the hypothesis that the cholinergic projection to the hippocampus facilitates the acquisition of information into the system responsible for short-term memory for locations visited (spatial working memory) but is not involved in retention of this information. It also appears to play no role in either the acquisition or retention of place-nonreward associations (spatial reference memory).

Animals↗
PubMed1996

Positional cloning of a novel potassium channel gene: KVLQT1 mutations cause cardiac arrhythmias.

Genetic factors contribute to the risk of sudden death from cardiac arrhythmias. Here, positional cloning methods establish KVLQT1 as the chromosome 11-linked LQT1 gene responsible for the most common inherited cardiac arrhythmia. KVLQT1 is strongly expressed in the heart and encodes a protein with structural features of a voltage-gated potassium channel. KVLQT1 mutations are present in affected members of 16 arrhythmia families, including one intragenic deletion and ten different missense mutations. These data define KVLQT1 as a novel cardiac potassium channel gene and show that mutations in this gene cause susceptibility to ventricular tachyarrhythmias and sudden death.

Amino Acid Sequence↗
PubMed1996

Susceptible chiasmate configurations of chromosome 21 predispose to non-disjunction in both maternal meiosis I and meiosis II.

The cause of non-disjunction of chromosome 21 remains largely unknown. Advanced maternal age is associated with both maternal meiosis I (MI) and meiosis II (MII) non-disjunction events. While reduced genetic recombination has been demonstrated in maternal MI errors, the basis for MII errors remains uncertain. We studied 133 trisomy 21 cases with maternal MII errors to test the hypothesis that segregation at MII may also be influenced by genetic recombination. Our data support a highly significant association: MII non-disjunction involves increased recombination that is largely restricted to proximal 21q. Thus, while absence of a proximal recombination appears to predispose to non-disjunction in MI, the presence of a proximal exchange predisposes to non-disjunction in MII. These findings profoundly affect our understanding of trisomy 21 as they suggest that virtually all maternal non-disjunction results from events occurring in meiosis I.

Adult↗
PubMed1996

Enhanced diallyl trisulfide has in vitro synergy with amphotericin B against Cryptococcus neoformans.

Although amphotericin B remains the drug of choice for systemic fungal infections, its use is limited by considerable side effects. In The Peoples' Republic of China, commercial Allium sativum derived compounds are widely used as an antifungal drug to treat systemic fungal infections. To evaluate the scientific merit of using A. sativum derived compounds as antifungal agents, we studied a Chinese commercial preparation, allitridium. This preparation contained mainly diallyl trisulfide as confirmed by high performance liquid chromatography. Allitridium, with and without amphotericin B, was tested to determine its efficacy in killing three isolates of Cryptococcus neoformans. The minimum inhibitory concentration of the commercial preparation was 50 micrograms/ml and the minimum fungicidal concentration was 100 micrograms/ml against 1 x 10(5) organisms of C. neoformans. In addition, the commercial preparation was shown to be synergistic with amphotericin B in the in vitro killing of C. neoformans. This study demonstrates that diallyl trisulfide and other polysulfides possess potent in vitro fungicidal effects and their activity is synergistic with amphotericin B. These observations lend laboratory support for the treatment of cryptococcal infections with both amphotericin B and the Chinese commercial preparation.

Allyl Compounds↗
PubMed1996

Modelling urban-rural population growth in China.

"The population of China is still growing despite a dramatic decline in fertility in the past two decades. There are marked urban-rural differentials in fertility and, as a result, the pace of urbanization has significant effects on population growth. In this research an attempt is made to model urban-rural population growth in China. A demoeconomic model of urban and rural sectors is calibrated to account for the long-term trend of urbanization in China.... An accounts-based urban-rural population model, in which rural to urban migration and transition are driven by the foregoing demoeconomic model, is established.... These models are used to make urban-rural population projections for the period 1988-2087 under various fertility rate assumptions."

Asia↗
PubMed1996

Priming effect of substrate addition in soil-based biodegradation tests.

To test whether substrate addition changes background CO2 evolution of soil, we measured both 14CO2 and net CO2 evolution from various test compounds. Glucose caused a priming effect, defined as substrate-stimulated soil organic matter mineralization. Formate, benzoate, n-hexadecane, and bis(2-ethylhexyl)phthalate caused no priming, and phenol caused only a transient one. The priming effect of glucose appears to be unusual and does not require a general rejection of net CO2 evolution measurements in biodegradability testing.

Biodegradation, Environmental↗
PubMed1996

Metabolic efficiency and turnover of soil microbial communities in biodegradation tests.

Biodegradability screening tests of soil commonly measure 14CO2 evolution from radiolabeled test compounds, and glucose has often served as a positive control. When constant amounts of radiolabel were added to soil in combination with increasing amounts of unlabeled substrates, glucose and some related hexoses behaved in an anomalous manner. In contrast to that of formate, benzoate, n-hexadecane, or bis(2-ethylhexyl) phthalate, dilution of glucose radiocarbon with unlabeled glucose increased rather than decreased the rate and extent of 14CO2 evolution. [14C]glucose incorporation into biomass and Vmax values were consistent with the interpretation that application of relatively high concentrations of glucose to soil shifts the balance of the soil microbial community from the autochthonous (humus-degrading) to the zymogeneous (opportunistic) segment. The higher growth and turnover rates that define zymogeneous microorganisms, combined with a lower level of carbon incorporation into their biomass, result in the evolution of disproportionate percentages of 14CO2. When used as positive controls, glucose and related hexoses may raise the expectations for percent 14CO2 evolution to levels that are not realistic for other biodegradable compounds.

Biodegradation, Environmental↗