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Biomedical subjects

X M Cheng

Publications and source records attributed to X M Cheng.

At least 19 recordsLinked to original sources
PubMed2005

Antisymmetric magnetoresistance in magnetic multilayers with perpendicular anisotropy.

While magnetoresistance (MR) has generally been found to be symmetric in applied field in nonmagnetic or magnetic metals, we have observed antisymmetric MR in Co/Pt multilayers. Simultaneous domain imaging and transport measurements show that the antisymmetric MR is due to the appearance of domain walls that run perpendicular to both the magnetization and the current, a geometry existing only in materials with perpendicular magnetic anisotropy. As a result, the extraordinary Hall effect gives rise to circulating currents in the vicinity of the domain walls that contributes to the MR. The antisymmetric MR and extraordinary Hall effect have been quantitatively accounted for by a theoretical model.

Journal Article↗
PubMed2001

Longitudinal study of blood pressure and stroke in over 37,000 People in China.

As part of a longitudinal study performed in urban China, 37,655 subjects were evaluated for stroke risk factors, including having their blood pressure measured in a standard fashion. The cohort was followed for 3.5 years during which time 427 subjects experienced incident strokes--221 ischemic, 203 hemorrhagic, and 3 undefined. Both systolic and diastolic blood pressure were significantly related to risk of stroke and stroke type. Associations were stronger for systolic than diastolic blood pressure. These results emphasize the importance of systolic blood pressure, as opposed to diastolic, as a risk factor for stroke. In this study, the risk of stroke is increased by about 25% with each 10 mm Hg increase in systolic blood pressure.

Adult↗
PubMed2001

[Determination of ciprofloxacin in urine using terbium ion as fluorescent probe].

Factors effecting the fluorescence characteristics of the reaction CPFX-Tb were studied thoroughly. The effect of the experimental conditions on the fluorescence intensity was defined. In the pH 6.0 media, CPFX-Tb complex fluorescence system can emit intrinsic fluorescence of Tb. The excitation and emission wavelengths are 328 nm and 545 nm. The linear range is 1.0 x 10(-8)-1.0 x 10(-6) mol.L-1. The regression equation is F = 1.57 + 4.87 x 10(8) c, r = 0.9999 with the detection limit of 5.0 x 10(-9) mol.L-1. It has been satisfactory for the determination of trace ciprofloxacin in urine by using terbium ion as fluorescent probe.

Anti-Infective Agents↗
PubMed2000

Vascular anatomic variations in second toe transfers.

To devise a new classification of vascular variations in second toe transfer we analyzed the anatomic details of the first dorsal metatarsal artery in 304 cases of second toe transplantation and the venous structure in 200 cases. According to location, the arterial vascularity was classified as superficial (18% of cases), intramuscular (54%), inframuscular (23%), and absent (5%). According to diameter, it was classified into large (16%), medium (64%), and small (20%). Based on branching pattern, the artery was classified into ramifying type (88%), main trunk (4%), and fine branch type (8%). The venous drainage of the second toe was categorized as greater saphenous vein main trunk type, greater saphenous vein fine branch type, dorsal digital vein main trunk type, and dorsal digital vein fine branch type. Variations of the first dorsal metatarsal artery are common. Classification should be done according to its location, diameter, and branching pattern at the toe web. Regardless of location, big vessels entering the second toe are the most important attribute for successful outcome.

Adolescent↗
PubMed1999

Butenolide endothelin antagonists with improved aqueous solubility.

Continued development around our ETA-selective endothelin (ET) antagonist 1 (CI-1020) has led to the synthesis of analogues with improved aqueous solubility profiles. Poor solubility characteristics displayed by 1 required a complex buffered formulation in order to conduct iv studies. To overcome the use of specific iv formulations for preclinical studies on additional drug candidates, analogues with improved aqueous solubility were desired. Several analogues were synthesized with substitution patterns that allowed for the formation of either acid or base addition salts. These derivatives had dramatically improved aqueous solubility. In addition, these analogues retained equivalent or improved ETA receptor selectivity and antagonist potency, versus 1, both in vitro and in vivo. Compound 29, which contains as a substituent the sodium salt of a sulfonic acid, has an ETA IC50 = 0.38 nM, ETA selectivity of 4200-fold, and ETA functional activity of KB = 7.8, all of which are similar or superior to those of 1. Compound 29 also has vastly superior aqueous solubility and solubility duration, compared to 1. Furthermore, 29 after iv infusion displays improved activity to 1 in preventing acute hypoxia-induced pulmonary hypertension in rats with an ED50 = 0.3 microg/kg/h.

Animals↗
PubMed1999

Prevention of stroke in urban China: a community-based intervention trial.

BACKGROUND AND PURPOSE: Stroke has been the second leading cause of death in large cities in China since the 1980s. Meanwhile, the prevalences of hypertension and smoking have steadily increased over the last 2 decades. Therefore, a community-based intervention trial was initiated in 7 Chinese cities in 1987. The overall goal of the study was to evaluate the effectiveness of an intervention aimed at reducing multiple risk factors for stroke. The primary study objective was to reduce the incidence of stroke by 25% over 3.5 years of intervention. METHODS: In May 1987 in each of 7 the cities, 2 geographically separated communities with a registered population of about 10 000 each were selected as either intervention or control communities. In each community, a cohort containing about 2700 subjects (>/=35 years old) free of stroke was sampled, and a survey was administered to obtain baseline data and screen the eligible subjects for intervention. In each city, a program of treatment for hypertension, heart disease, and diabetes was instituted in the intervention cohort (n approximately 2700) and health education was provided to the full intervention community (n approximately 10 000). A follow-up survey was conducted in 1990. Comparisons of intervention and control cohorts in each city were pooled to yield a single summary. RESULTS: A total of 18 786 subjects were recruited to the intervention cohort and 18 876 to the control cohort from 7 cities. After 3.5 years, 174 new stroke cases had occurred in the intervention cohort and 253 in the control cohort. The 3.5-year cumulative incidence of total stroke was significantly lower in the intervention cohort than the control cohort (0.93% versus 1.34%; RR=0.69; 95% CI, 0.57 to 0.84). The incidence rates of nonfatal and fatal stroke, as well as ischemic and hemorrhagic stroke, were significantly lower in the intervention cohort than the control cohort. The prevalence of hypertension increased by 4.3% in the intervention cohort and by 7.8% in the control cohort. The average systolic and diastolic blood pressures increased more in the control cohort than in the intervention cohort. Among hypertensive individuals in the intervention cohort, awareness of hypertension increased by 6.7% and the percentage of hypertensives who regularly took antihypertensive medication increased 13.2%. All of these indices became worse in the control cohort. The prevalence of heart diseases and diabetes increased significantly in the both cohorts (P<0.01). The prevalence of consumption of alcohol increased slightly, and that of smoking remained constant in both cohorts. CONCLUSIONS: A community-based intervention for stroke reduction is feasible and effective in the cities of China. The reduction, due to the intervention, in the incidence of stroke in the intervention cohort was statistically significant after 3.5 years of intervention. The sharp reduction in the incidence of stroke may be due to the interventions having blunted the expected increase in hypertension that accompanies aging as well as to better and earlier treatment of hypertension, particularly borderline hypertension. Applied health education to all the residents of the community may have prevented some normotensive individuals from developing hypertension and improved overall health awareness and knowledge.

Cerebrovascular Disorders↗
PubMed1999

[Electrophysiological criteria for selection of operative procedure in the treatment of late incomplete obstetrical palsy].

OBJECTIVE: Using electrophysiological method to evaluate the severity of incomplete obstetric paralysis brachial plexus injuries, and establish an electrophysiological criteria for selection of operative procedure in the treatment of cases of late stage. METHODS: Neurolysis was performed in 16 patients, and during the operation, the neuroma at the upper trunk was discovered. The electrophysiological study was carried out before and during operation to evaluate the conducting function of neuroma. In the follow-up the operative result was analysed by Mallet test. RESULTS: The preoperative study showed that the compound muscular active potential (CMAP) amplitude of supraspinatus deltoid and biceps were decreased more than 60% in comparison with that of the healthy side. After external neurolysis of the neuroma, by stimulation of the proximal and distal ends of the neuroma the average decrease of CMAP amplitude of the above three muscles was 37.45% +/- 20.97%, 47.85% +/- 26.23%, 47.05% +/- 21.23%, respectively and no significant improvement was observed in the shoulder and elbow function in all of the 16 cases. CONCLUSION: When the preoperative electrophysiological study found that the CMAP amplitude decreased more than 60% in comparison with that of the healthy side, transposition of nerve or nerve grafting was indicated.

Birth Injuries↗
PubMed1999

[The emergent repair of peripheral nerve injury of the wrist].

OBJECTIVE: To investigate the effect of the emergent repair of peripheral nerve injury of the wrist. METHODS: From July 1993 to December 1997, 17 cases were admitted, which 21 injured peripheral nerves were repaired emergently. Among them, there were 11 cases of median nerve injury, 2 cases of ulnar nerve injury and 4 cases of median and ulnar nerve injury. All the nerves were ruptured completely except one which was partially ruptured. The emergent operation was taken and the injured nerves were repaired by microsurgical technique. RESULTS: Followed up 6 to 18 months after operation, 95.25% injured nerves had good outcome. CONCLUSION: Because of the specific structure of the wrist, nerve injury at this part need to be repaired emergently. It can enhance the regeneration of the injured nerve, preserve the function of the intrinsic muscle of hand, and decrease the local adhesion.

Adolescent↗
PubMed1998

Novel selective quinazoline inhibitors of endothelin converting enzyme-1.

PD 069185 is a highly selective and structurally novel inhibitor of endothelin converting enzyme-1 (ECE-1). PD 069185 is a trisubstituted quinazoline with an IC50 value of 0.9 +/- 0.1 microns for inhibition of human ECE-1 from the solubilized membrane fraction of CHO cells stably transfected with human ECE-1 cDNA. Kinetic analysis revealed that PD 069185 is best fit with a competitive inhibition model with a Ki value of 1.1 +/- 0.1 microns and binds in a reversible manner. The closely related enzyme, ECE-2, is not inhibited at up to 100 microns PD 069185. In addition, PD 069185 at 200-300 microns has little effect on other metalloproteases, such as neutral endopeptidase 24.11, stromelysin, gelatinase A, and collagenase, showing a high ECE-1 specificity. Data are also presented to show that this series of inhibitors are effective in inhibiting ECE-1 in intact cells and in attenuating the increase in perfusion pressure induced by big ET-1 in isolated rat mesentery. These non-peptidic ECE-1 inhibitors should serve as a valuable tool to study the pathophysiological role of endothelin and the therapeutic potential of ECE-1 inhibitors.

Animals↗
PubMed1998

Long-term functional results of contralateral C7 transfer.

From 1986 to 1994, 82 patients with brachial plexus root avulsion were operated on using a contralateral C7 nerve-root transfer. Forty-four patients underwent a one-stage procedure in which the distal end of the ulnar nerve was anastomosed to the contralateral C7 root, and the other 38 underwent a two-stage procedure (first phase: C7 root --> ulnar nerve; second phase: ulnar nerve --> recipient nerve). Twenty postoperative cases were followed-up for 2 years. Of them, the ulnar nerve was transferred to the musculocutaneous nerve in six cases, with recovery of the biceps up to M3 in four and S3 in five cases; the ulnar nerve was transferred to the median nerve in eight cases, with recovery of the wrist and finger flexors up to M3 in five and S3 in six cases; the ulnar nerve was transferred to the radial nerve in four cases, with recovery of the triceps up to M4 in two and S3 in three cases; and the ulnar nerve was transferred to the thoracodorsal nerve in two cases, with recovery of the latissimus dorsi to M4 in one case. The total muscle recovery rate (up to M3) of the series was 60 percent, and the sensory recovery rate (S3) was 78 percent. Outcomes were related to patient age, operative delay, and whether or not the ulnar nerve was used as a bridge for transfer.

Adolescent↗
PubMed1998

Endothelin B receptors on human endothelial and smooth-muscle cells show equivalent binding pharmacology.

We have described the pharmacologic profiles of endothelin B receptors in human endothelial cells and vascular and nonvascular smooth-muscle cells. First, by amplifying endothelin B receptor numbers through the use of phosphoramidon and intact cell-binding techniques, we demonstrated the presence of these receptors in human umbilical vein endothelial cells (100% endothelin B receptors), human aortic smooth-muscle cells (22% endothelin B, 78% endothelin A receptors), and human bronchial smooth-muscle cells (55% endothelin B, 45% endothelin A receptors) by using [125I]-endothelin-1 radioligand binding. The typical binding profiles of the endothelin B receptors were established through competition binding curve analysis with endothelin-1, endothelin-3, sarafotoxin 6c, and the endothelin A receptor-selective antagonist BQ-123. In the presence of BQ-123, a diverse group of antagonists, including PD 142893, BQ-788, SB 209670, and Ro 47-0203, were used to probe for binding differences indicative of multiple endothelin B-receptor subtypes. The results indicate a rank order of potency for the antagonists of BQ-788 > SB 209670 > PD 142893 > Ro 47-0203 for each cell line, and that between any of these human cell lines, measurements of [125I]-endothelin-1-binding antagonism for each of the four test compounds differed by less than twofold. Although this study cannot discount the possibility of more than one endothelin B-receptor subtype in humans, it does indicate that these tissues express receptors that show equivalent binding pharmacology.

Binding, Competitive↗
PubMed1998

PD 142893, SB 209670, and BQ 788 selectively antagonize vascular endothelial versus vascular smooth muscle ET(B)-receptor activity in the rat.

The purpose of this study was to determine whether vascular endothelial and vascular smooth-muscle endothelin ET(B) receptors could be quantitatively differentiated by PD 142893 (PD), SB 209670 (SB), and BQ 788 (BQ) in the same species by using closely matched experimental conditions. The isolated perfused rat kidney (vascular smooth muscle) and isolated perfused rat mesentery (vascular endothelium) were challenged with increasing bolus doses of sarafotoxin S6c in the absence and presence of antagonist. PD, SB, and BQ produced parallel concentration-dependent rightward shifts in the S6c dose-response curve in the kidney. PD and SB also produced parallel concentration-dependent rightward shifts in the S6c dose-response curve in the mesentery. In contrast, BQ produced an insurmountable antagonism. Schild-derived pA2 values for PD and SB were significantly greater for inhibiting endothelial versus smooth-muscle ET(B) receptors. Furthermore, PD and SB differed in their relative potency between the two assays. Because BQ produced an insurmountable antagonism in the mesentery, it was not possible quantitatively to compare the antagonist activity in the two assays. These results indicate that PD, SB, and BQ selectively antagonize endothelial ET(B)-receptor activity over smooth-muscle ET(B)-receptor activity.

Animals↗
PubMed1998

Femoral nerve transfer for treatment of brachial plexus root avulsion.

Femoral nerve transfer to the muscular branches of the thenar and hypothenar muscles was performed to determine its protective effect on the hand intrinsic muscles. Seven cases of brachial plexus root avulsion treated from May of 1989 to October of 1991 were involved. The femoral nerve transfer to the muscular branches of the thenar and hypothenar muscles was done at the same stage of multiple neurotization. The muscular branches derived from the femoral nerve were isolated and coapted with the thenar muscle branch of the median nerve and the deep branch of the ulnar nerve. A groin flap was harvested simultaneously to form a skin-tube pedicle that covered the nerve bridge. At the second stage, when regeneration of the median and ulnar nerves was found to reach as far as the level of the wrist, the femoral nerve was divided and the muscular branches of the thenar and hypothenar muscles were anastomosed with the regenerated median and ulnar nerves. All the cases were followed up for more than 6 years. Six months after femoral nerve transfer, muscle power of the interosseous muscles and adductor pollicis recovered to MRC3, whereas that of the abductor pollicis brevis recovered to MRC1 to 2. Five cases underwent second-stage transfer. Four to five years of follow-up revealed that the muscle power of the interosseous muscles and adductor pollicis was MRC2 in one case, MRC1 in three cases, and MRC0 in one case. As for the donor area, muscle power of the quadriceps femoris reduced to M3 to 4 within 1 month after femoral nerve transfer and recovered to normal at 3 months. In conclusion, femoral nerve transfer to the muscular branches of the thenar and hypothenar muscles has some protective effect on the hand intrinsic muscles. The outcome of the second stage, however, is not satisfactory.

Adolescent↗
PubMed1997

Cardiopulmonary indications for endothelin receptor antagonists: review of recent efficacy trials.

Recent clinical and experimental animal trials indicate that endogenously produced endothelin-1 (ET-1) contributes to the abnormal systemic and pulmonary vascular resistance associated with congestive heart failure (CHF) and pulmonary hypertension (PH). In experimental CHF, the chronic blockade of ET-1 actions by ET receptor antagonists clearly improves haemodynamic status, and improves cardiac structure and survival. The latter is based on limited results. In experimental PH there are consistent reports of prevention and reversal of PH, pulmonary vascular remodelling and right ventricular hypertrophy, independent of the inciting mechanisms. These results in experimental animals illustrate the potential efficacy of the ET receptor antagonists in future clinical trials. With five ET receptor antagonists in clinical development, and more on the way, their potential will soon be realised.

Journal Article↗
PubMed1996

Novel drimane sesquiterpene esters from Aspergillus ustus var. pseudodeflectus with endothelin receptor binding activity.

A series of novel drimane sesquiterpene esters (1-6) was isolated from fermentations of Aspergillus ustus var. pseudodeflectus and their structures elucidated by spectroscopic methods including the HMQC, HMBC and INADEQUATE NMR experiments. The major component of the fermentation, 1, was (2'E,4'E,6'E)-6-(1'-carboxy-2',4',6'-trien)-9-hydroxydrim-7-ene-11 ,12-olide. Compounds 1, 2, 3 and 5 exhibited endothelin receptor binding inhibitory activity against rabbit endothelin-A and rat endothelin-B receptors with IC50 values in the range 20-150 microM. These compounds had similar levels of activity in assays for binding to human endothelin A and endothelin B receptors. The isolation of 9,11-dihydroxy-6-oxodrim-7-ene, 7, a probable biosynthetic precursor to the drimane esters is also reported.

Animals↗
PubMed1995

The social course of epilepsy: chronic illness as social experience in interior China.

Findings are reported from a collaborative research project on the experience of epilepsy and treatment among patients and family members in Shanxi and Ningxia Provinces in China. Family, marriage, financial and moral consequences of the social experience of epilepsy support the conceptualization of chronic illness as possessing a social course. Beyond traditional concern with stigma, application of concepts of delegitimation, sociosomatic processes, coping as resistance, contestation in the evaluation of efficacy and compliance, and the cultural ontology of suffering illustrate other ways that social theory is useful in research on chronic illness and disability.

Adaptation, Psychological↗
PubMed1995

Stroke in China, 1986 through 1990.

BACKGROUND AND PURPOSE: Incidence of stroke varies markedly in different world populations. In seven Chinese cities, the effect of a program of risk factor modification on the incidence and mortality of stroke was studied and compared with a control population. This article describes the incidence of stroke in the control populations for the years 1986 through 1990. METHODS: Incidence (first-ever strokes only) for 1986 was obtained by door-to-door interview with heads of households with subsequent verification on examination by a neurologist and review of medical and/or hospital records. In subsequent years, cases were ascertained with a three-tier monitoring system: by community health workers, local medical centers, and the Beijing Neurosurgical Institute. RESULTS: Average annual age-adjusted incidence per 100,000 was 215.6 (261.5 for males, 174.5 for females; P < .001). There was a significant drop in the total number of cases from 137 in 1986 to 106 in 1990, but the age-adjusted rate showed a significant drop for males only (322.3 to 182.5, P < .001). Marked differences in average annual age-adjusted rates existed among the seven cities, from 486.4 for Harbin to 80.9 for Shanghai. This difference in rate among cities was found for both sexes but was more pronounced in males. CONCLUSIONS: The stroke incidence rates in China, like those in Japan, are among the higher ones in the world. In recent years, there has been an apparent decline in stroke incidence. Marked differences in rates were found between males and females with decline in incidence occurring almost exclusively in males. There were also marked differences in stroke incidence among the cities studied. These differences may result in part from differences in diet, alcohol and cigarette consumption, or prevalence of hypertension.

Adolescent↗