PubMed Health⌕ Search

Biomedical subjects

W Yuan

Publications and source records attributed to W Yuan.

At least 109 records · Page 6Linked to original sources
PubMed1998

Glutathione transferase T1 and M1 genotype polymorphism in the normal population of Shanghai.

Glutathione transferases are known to be important enzymes in the metabolism of xenobiotics. In humans genetic polymorphisms have been reported for the hGSTM1 and hGSTT1 genes leading to individual differences in susceptibility towards toxic effects, such as cancer. This study describes the distribution of the two polymorphisms of hGSTT1 and hGSTM1 in the normal Chinese population of Shanghai. Out of 219 healthy individuals having been genotyped for GSTT1 and GSTM1, 108 (49%) were identified to be homozygously deficient for the GSTT1 gene and 107 (49%) for the GSTM1 gene.

Adult↗
PubMed1998

Application of a new serum assay for type I collagen cross-linked N-telopeptides: assessment of diurnal changes in bone turnover with and without alendronate treatment.

Biochemical markers of bone turnover are finding increased application in the investigation and management of skeletal diseases such as osteoporosis. The present study assessed for the first time the diurnal variation of serum type I collagen cross-linked N-telopeptides (NTx), a new serum-based marker of bone resorption, and the effect of antiresorptive therapy with alendronate on this marker in elderly osteopenic women. The concentrations of serum NTx were monitored over 24 hours in a randomly selected subset of 38 women (placebo n = 13, 69 +/- 3 (SD) year; alendronate n = 25, 69 +/- 3 year), who had completed 12-15 months of a larger (n = 120) randomized, double-blind, parallel group, placebo-controlled trial with alendronate 5 mg/day. Blood was obtained every 4 hours for measurement of serum NTx using a new chemiluminescent-based immunoassay. There was a significant diurnal variation of serum NTx (p = 0.001) in both the placebo and alendronate groups. Mean peak levels occurred at approximately 0504 h with a mean nadir at approximately 1320 h in the placebo group, with no significant difference on alendronate. Serum NTx was approximately 25% lower in the alendronate group over the entire 24-hour period. Mean (SE) daytime (0800-2000) and nighttime (2200-0800) serum NTx values were 6.40 +/- 0.30 versus 8.45 +/- 0.58 nmol BCE/liter, and 7.42 +/- 0.23 versus 10.01 +/- 0.53 nmol BCE/liter for alendronate versus placebo, respectively (P < or = 0.003 for both comparisons). Combining the data of both treatment groups, serum NTx was significantly (P < 0.05) correlated with serum osteocalcin (r = 0.753) and urine NTx (r = 0.628) measurements previously obtained over the entire 24-hour period. Serum NTx has a significant diurnal variation and is responsive to antiresorptive therapy with alendronate. Alendronate reduces the amplitude but maintains the pattern of the 24-hour serum NTx profile. These data suggest that serum NTx may be a useful new marker of bone resorption.

Aged↗
PubMed1998

The efficacy of safety policies on traffic fatalities in Singapore.

This paper uses regression models to investigate the efficacy of the seat belt regulation as well as the circuit training and testing system in reducing traffic related fatalities in Singapore. The effectiveness of alcohol breathalysers was also studied. Results suggest that the seat belt regulation does not have any impact on traffic fatalities. The use of breathalysers was found to be effective in reducing occupant fatalities. The circuit training and testing system, which aims to equip new pools of motorists with appropriate driving or riding skills, was found to be effective in reducing non-occupant fatalities and total fatalities.

Accidents, Traffic↗
PubMed1998

Evidence for separate control of slow version and vergence eye movements: support for Hering's Law.

When a visual stimulus changes direction and distance simultaneously, Hering's Law argues that the resulting eye movements are the result of combined version and vergence control processes. Recently, it has been suggested that slow asymmetrical eye movements might be guided by monocular control processes wherein each eye is driven by its own retinal image. Experimental results presented here show behavioral differences between slow version and slow vergence eye movements, indicating that different control processes drive the two "pure" responses. Specifically, version tracking of constant velocity stimuli (i.e., smooth pursuit) is more precise, showing less variation in tracking velocity than movements of equal velocity produced by vergence stimuli. When the two stimuli are combined, the variability in tracking is consistent with the addition of the two components in proportion to their respective stimuli. These results provide support for Hering's Law, at least for low velocity, smooth tracking movements (i.e., slow version and slow vergence.

Adult↗
PubMed1998

Follicular dominance in cattle is associated with divergent patterns of ovarian gene expression for insulin-like growth factor (IGF)-I, IGF-II, and IGF binding protein-2 in dominant and subordinate follicles.

A decrease in insulin-like growth factor (IGF) binding protein (BP) amount occurs within the follicular fluid of dominant ovarian follicles. At the same time, concentrations of follicular fluid IGF-I do not change. The mRNA for IGF-I, IGF-II, IGFBP-2, and IGFBP-3, in dominant and subordinate follicles were measured to determine if changes in IGF or IGFBP gene expression are associated with follicular dominance. Heifers were ovariectomized during a follicular wave, either during early-dominance (emerging dominant follicle, 9 mm diameter) or mid-dominance (established dominant follicle, 14-16 mm diameter). Follicles were classified as either dominant (DF), subordinate (SF), or not-recruited (NRF; small antral follicles). mRNA was localized by in situ hybridization and measured by image analyses. The IGF-I mRNA (granulosa cells) was greatest in DF and increased in DF, SF, and NRF from early- to mid-dominance. Likewise, IGF-II mRNA (theca cells) was greatest in DF compared with SF or NRF. The IGFBP-2 mRNA (granulosa cells), however, was nearly undetectable in DF, whereas adjacent SF expressed abundant IGFBP-2 mRNA. The NRF were not uniform in their IGFBP-2 expression because only 5 of 13 NRF had IGFBP-2 mRNA. The IGFBP-3 mRNA (granulosa cells) was found only in two NRF, suggesting that local synthesis is not a predominant source of follicular fluid IGFBP-3. These data show that changes in gene expression for IGFBP-2 are opposite to those for IGF-I or IGF-II. Increased IGF-I and IGF-II mRNA and decreased IGFBP-2 mRNA within the DF may be one mechanism leading to follicular dominance. The opposite pattern of IGFBP-2 gene expression in SF and some NRF may lead to follicular atresia.

Animals↗
PubMed1998

Closely spaced, fast dynamic movements in disparity vergence.

Conflicting theories exist describing how symmetrical vergence responses, the inward or outward turning of the eyes, are mediated. Classical theories describe vergence control as mediated by visual feedback. Extensive experimental evidence indicates that two distinct control components comprise the vergence response, and a recent theory supports the concept that one of these components is not visually guided. Occasionally, saccadic eye movements will respond to a single step stimulus with two closely spaced saccades, a behavior that is indicative of its switching control structure. If a portion of the vergence response is controlled in a manner analogous to saccades, then occasional double fast dynamic components might be expected. During this study, eye movements were recorded in response to symmetrical vergence stimuli of 2, 4, 6, 8, and 10 degrees steps. The left and right eye movements were subtracted to yield a net vergence response, and only convergent responses were investigated. Double fast dynamic components associated with high-velocity movements were observed in all four subjects studied. In double high-velocity component responses, the average peak velocity of both fast dynamic movements was always considerably less than the average peak velocity found when the response to the same stimulus was made with only a single component. Response amplitudes of single and double movements showed that if the primary component of a double response did not reach >/=80% of the stimulus amplitude, a secondary component would be generated to aid the movement. Plots of peak velocity as a function of response amplitude for both double and single movements followed the main sequence for vergence eye movements demonstrating that the first-order dynamic characteristics of all high-velocity components were the same. The time at which maximum velocity occurred (relative to stimulus onset) was also the same for both single component responses and the first component of double responses. The similarity in dynamics and timing implies that the high-velocity components were processed by the same controller mechanism. The existence of double high-velocity movements is indicative of an internal, switching mechanism similar to that found in saccades and is difficult to explain with theories that rely on visual feedback control alone.

Calibration↗
PubMed1998

Radiculopathy after laminectomy for cervical compression myelopathy.

Postoperative radiculopathy is a complication of posterior cervical decompression associated with tethering of the nerve root. We reviewed retrospectively 287 consecutive patients with cervical compression myelopathy who had been treated by multilevel cervical laminectomy and identified 37 (12.9%) with postoperative radiculopathy. There were 27 men and ten women with a mean age of 56 years at the time of operation. The diagnosis was either cervical spondylosis (25 patients) or ossification of the posterior longitudinal ligament (12 patients). Radiculopathy was observed from four hours to six days after surgery. The most frequent pattern of paralysis was involvement of the C5 and C6 roots of the motor-dominant type. The mean time for recovery was 5.4 months (two weeks to three years). The results at follow-up showed that the rate of motor recovery was negatively related to the duration of complete recovery of postoperative radiculopathy (gamma=-0.832, p < 0.01) and that patients with spondylotic myelopathy had a significantly better rate of clinical recovery than those with ossification of the posterior longitudinal ligament (t=2.960, p < 0.01). Postoperative radiculopathy may be prevented by carrying out an anterior decompression in conjunction with spinal fusion, which will achieve stabilisation and directly remove compression of the cord at multiple levels.

Adult↗
PubMed1998

Diagnosis and treatment of acute central cervical cord injury.

OBJECTIVE: To clarify the diagnosis and management of acute central cervical cord injury. METHODS: Eighty-nine patients with acute cervical central cord injury were retrospectively reviewed. Sixty-three patients were treated conservatively and 26 were treated surgically. There were two acute deaths. Eighty-seven patients were followed up for 3 months to 15 years. RESULTS: Their average neurological score (ASIA) was increased from 41.7 at admission to 83.1 at follow-up. CONCLUSIONS: Acute central cervical cord injury should be differentiated from complete spinal cord injury, cervical myelopathy, cruciate paralysis and C8 nerve root injury. When compression of nerve tissue or cervical instability is identified, operative intervention should be indicated. The prognosis is less optimistic in the patients with severe primary injury and at old age.

Adult↗
PubMed1998

[Study of physiological parameters of velopharyngeal function by nasopharyngeal fibroscope].

OBJECTIVE: Velopharyngeal incompetency (VPI) could be found in certain healthy people when some vowels were produced. Since neither asophia nor organic deformity do they have, it should be considered as physiological VPI. VPI which exists commonly in patients with cleft palate is also an unsatisfactory manifestation after palatoplasty. In order to distinguish between physiological VPI and pathological VPI in patient with cleft palate and establish an objective criterion, it is necessary to assess the occurrence and extent of VPI in healthy people. METHODS: The velopharyngeal function of 890 subjects with normal speech was studied dynamically by nasopharyngeal fiberscope (NPF). Two vowels /i/ and /u/ were examined. The rates of velopharyngeal incompetence (RVPI) of vowel /i/ and /u/ were analyzed. RESULTS: VPI was found in 117 (13.15%) when vowel /i/ was produced. VPI was occurred in 100 (11.24%) when /u/ was produced. The RVPI mean of vowel /i/ is 11.285% +/- 7.248 in 112 subjects, while that of /u/ is 9.066% +/- 6.162 in 96. No significant difference was obtained in age or sex. CONCLUSION: It can be used to evaluate the velopharyngeal function after palatoplasty as physiological parameters.

Adult↗
PubMed1998

[Quantitative analysis of velopharyngeal function by nasopharyngeal fibroscope (NPF)].

OBJECTIVE: To estimate the reliability of the nasopharyngeal fibroscope (NPF) for assessing velopharyngeal function. METHODS: 16 well-pronounced males were examined by NPF which was positioned in different depth. Same procedures were repeated after a week. RESULTS: The results indicated that the rate of velopharyngeal incomptence (RVPI) of NPF had no significant difference when checked in different time and various depths. CONCLUSION: RVPI can be used as a parameter of quantitative analysis for velopharyngeal function, and our results suggested that it is reliable and reproduciable.

Endoscopes↗
PubMed1998

[Cervical spondylotic myelopathy: early diagnosis and timing of operation].

OBJECTIVES: To study early clinical characteristics and diagnosis of cervical spondylotic myelopathy and to search the timing of surgery. METHOD: Seventy-four cases of early diagnosed cervical spondylotic myelopathy (CSM) were treated with anterior cervical decompression and autologous ilium graft fusion. RESULT: The early stage of CSM was indistinct, and symptoms were mild. Neck pain, abnormality of motion and sensation of limbs, and hand and arm symptoms were shown frequently. Changes in neurological function could found during physical examination. Characteristic changes in imaging were helpful in early diagnosis of the disease. CONCLUSION: Early diagnosis and surgery of CSM are important in improving the therapeutic results.

Adult↗
PubMed1998

[The effects of graded spinal cord injuries on transcranial electric stimulation motor evoked potentials in the rat].

OBJECTIVE: To study the effects of graded spinal cord injury (SCI) on the motor evoked potentials (MEP) characteristics and the prognostic value of MEP for the motor function. METHOD: Modified Allen's method was used by weight drop force of 30 gcf, 50 gcf, 80 gcf and 100 gcf on the T(8 - 9) spinal cord of 40 SD rats in order to make SCI models. MEP was recorded continuously at L(1 - 2) epidurally and bilateral gastrocnemius muscles before and after the spinal cord lesion was produced (followed up for 1 month). The inclined plane and Tarlov technique were used to assess clinical neurological function. RESULT: The amplitude of rat's MEP changed significantly with graded SCI, the more sever the lesion, the lower the potentials. mMEP was more sensitive than scMEP, though the abolishment of mMEP soon after SCI didn't indicate that the animals could not regain ambulation. Changes in amplitude of scMEP recorded early after SCI were collaborate significantly with inclined plane (gamma = 0.9665, P < 0.01) and Tarlov scale (gamma = 0.8893, P < 0.01) assessed 1 month later, and can be used as a chronic measure parameter of motor function prognosis. scMEP still existed 1 month after SCI in 3 of 11 rats (27.3%) without any voluntary movement in bilateral hindlimbs, suggesting that some parts of conductive function still existed in the spinal cord. So it should be called "discomplete SCI". CONCLUSIONS: scMEP can be used as a reliable parameter for motor function prognosis, because it reflects objectively and sensitively the severity of central motor neurol fiber injury.

Animals↗
PubMed1998

[Diagnosis and treatment of tethered cord syndrome in adults].

OBJECTIVE: To study the clinical characteristics of tethered cord syndrome (TCS) in adults. METHOD: 18 patients with TCS were confirmed by preoperative MRI and were operated on for releasing of tethered conus. Pathological mechanism and main points of operation were analysed according to the operative findings and radiological data. RESULT: The cord or conus were tethered by intradural tumors (6 patients), myelomeningocele (6), thickened filum terminale (3), diastematomyelia (2) and adhesion after operation (1). 14 of the 18 patients showed good results after follow-up for 8 months to 5 years. CONCLUSION: Clinical manifestation and prognosis of TCS in adults are different from those of TCS in children. Attention should be paid to avoid additional injury to the conus and cauda equina during operation. The long course of disease and retethering of the conus lead to poor outcome.

Adolescent↗
PubMed1998

[Clinical significance of early diagnosis of cervical spondylotic myelopathy].

OBJECTIVE: To probe into the possibility of early diagnosis of cervical spondylotic myelopathy (CSM) prospectively and to screen the premorbid signs of CSM clinically, radiologically and electro-physiologically. METHOD: Twenty-nine items related to the occurring of CSM were chosen as common characteristics of CSM and considered as the criteria of prospective study. 81 patients who met the criteria were studied. All patients were followed up and observed for 2 - 6.5 years (mean 3.7 years). RESULT: Twenty-nine patients showed CSM during investigation. Thirteen items of the criteria were related to the occurring of CSM. The significant items include upper limb pain and abnormal sensation limb numbness, positive dynamic Hoffmann's sign, cervical canal stenosis, lower cervical instability, cervical intervertebral disc herniation, and delay of central motor conduct time. CONCLUSION: CSM can be early diagnosed. The patients who meet the established criteria should be followed up and observed closely. Early operation results in good effect.

Adult↗
PubMed1998

[Experimental study of radiation effects on the mandibular microvasculature of the guinea-pigs].

In the experiment, both 180 kV X-ray and cobalt-60 radiation were delivered to right mandibles of 128 guinea-pigs with different dose (1000 cGy x 4, 800 cGy x 4, 600 cGy x 4, 400 cGy x 4 within 1 week). Dental extractions were conducted 1, 3, 5 months after radiation and the irradiated animals were examined by using microvascular corrosion castings of mandibles. It was found that the number of capillaries reduced and microvascular networks broke off after radiation with small veins shrinking subsequently while the alterations of arteries were slight. This result indicated that capillary was the most vulnerable part to the damage of radiation in the vascular system. In addition the defects of vascular networks around the non-healing tooth extraction sites were also discovered with irregularly capillary proliferation in the periphery of the lesion. The phenomena suggested that microcirculation failure induced by trauma-repairing process lead to occurRence of osteoradionecrosis of jaws.

Animals↗
PubMed1997

Ethylbenzene modulates the expression of different cytochrome P-450 isozymes by discrete multistep processes.

Ethylbenzene (EB) treatment to male Holtzman rats was shown to alter the expression of cytochrome P-450s 1A1, 2B, 2C11, 2E1, and 3A, with several isozymes exhibiting complex multiphasic induction patterns when treated for 1 and 3 days with the alkylbenzene. Male rats were treated with daily i.p. injections of EB for either one or three days, and the effects on P-450 dependent activities, P-450 immunoreactive protein levels and their corresponding mRNA levels were measured. Although levels of P-450 2B, 2C11, 2E1, and 3A were all modulated by EB treatment, each exhibited different temporal characteristics. P-450 2B1/2B2 were induced after a single EB exposure and continued to be elevated after EB treatment for 3 days. However, P-450 2B1 and 2B2 mRNA levels were elevated about 50-fold after a single injection, and returned to control values after continued EB administration. P-450 2C11 expression was decreased to about 45% of controls after either single or repeated EB exposure with corresponding changes being observed in the levels of 2C11 mRNA. P-450 2E1 was induced by EB according to a complex multistep induction pattern. Both P-450 2E1 protein and RNA levels were increased 2-4-fold after a single EB treatment but returned to control values after continued administration. P-450 3A-dependent testosterone 2beta-hydroxylation and P-450 3A immunoreactive protein levels were both increased about 3-fold after a single EB treatment, whereas levels were only elevated 2-fold after EB treatment for 3 days. In contrast, P-450 3A2 mRNA was unaffected by a single EB injection but was increased 3.5-fold with repeated administration. Changes in P-450 3A1/2 were similar to those observed with P-450 3A2, whereas changes in P-450 3A1/23 and 3A23 mRNAs were not detectable. These data indicate that while EB can influence the expression of several P-450 isozymes, the hydrocarbon appears to alter P-450 expression by acting at different regulatory steps.

Animals↗
PubMed1997

Time course for the modulation of hepatic cytochrome P450 after administration of ethylbenzene and its correlation with toluene metabolism.

The goal of the present study was to examine the time course for changes in P450 expression and hydrocarbon metabolism after acute treatment with the simple aromatic hydrocarbon ethylbenzene (EB) and to correlate these alterations with the changes observed in alkylbenzene metabolism. Male Holtzman rats were treated with a single intraperitoneal injection of EB, and the effects on specific P450-dependent activities, immunoreactive P450 isozyme levels, and RNA levels were measured at various times after injection. Toluene was used as the test alkylbenzene for examination of the EB-mediated changes on in vitro hydrocarbon metabolism. In untreated rats, toluene was metabolized almost entirely by aliphatic hydroxylation (to benzyl alcohol); however, in EB-treated rats, significant quantities of benzyl alcohol, o-cresol, and p-cresol were produced. Interestingly, 5-10 h after EB treatment, there was a 40% decrease in benzyl alcohol production. By 24 h, rates of benzyl alcohol formation returned to control levels, whereas there was a 7-fold increase in o-cresol and a greater that 50-fold increase in p-cresol production. The changes in the disposition of toluene were then correlated with changes in particular P450 isozymes. Several P450 isozymes were induced after EB administration. P450 2B1/2-dependent testosterone 16 beta-hydroxylation and P450 2B1/2-immunoreactive protein were elevated 30-fold after EB administration, reaching maxima by 24 h and remaining elevated 48 h after exposure. Changes in P450 2B1 and 2B2 RNA preceded those of the proteins. Similar results were observed with P450 1A1. P450 2E1 RNA levels were elevated after a single EB injection. However, the elevation in P450 2E1-dependent activities and immunoreactive protein levels preceded the changes in RNA, suggesting that multiple steps are affected by EB exposure. In contrast to the increases in some isozymes, P450 2C11 protein was rapidly suppressed (within the first 2-10 h) after hydrocarbon exposure, suggestive of a destabilization of the protein. When comparing the changes in P450 isozymes to alterations in toluene metabolism, the immediate suppression in aliphatic hydroxylation of toluene (in the first 5-10 h) was consistent with the decrease in P450 2C11. Subsequent to this effect, P450 2B1/2 and 2E1 were induced, which elevated production of this metabolite to control levels. The increase in the aromatic hydroxylation of toluene to both o, and p-cresol was consistent with the induction of P450s 2B1/2, 2E1, and 1A1.

Animals↗