Biomedical subjects

R Chen

Publications and source records attributed to R Chen.

At least 199 records · Page 11Linked to original sources

PubMed2000

The hemodynamic and adrenergic effects of perioperative dexmedetomidine infusion after vascular surgery.

UNLABELLED: We tested dexmedetomidine, an alpha(2) agonist that decreases heart rate, blood pressure, and plasma norepinephrine concentration, for its ability to attenuate stress responses during emergence from anesthesia after major vascular operations. Patients scheduled for vascular surgery received either dexmedetomidine (n = 22) or placebo (n = 19) IV beginning 20 min before the induction of anesthesia and continuing until 48 h after the end of surgery. All patients received standardized anesthesia. Heart rate and arterial blood pressure were kept within predetermined limits by varying anesthetic level and using vasoactive medications. Heart rate, arterial blood pressure, and inhaled anesthetic concentration were monitored continuously; additional measurements included plasma and urine catecholamines. During emergence from anesthesia, heart rate was slower with dexmedetomidine (73 +/- 11 bpm) than placebo (83 +/- 20 bpm) (P = 0.006), and the percentage of time the heart rate was within the predetermined hemodynamic limits was more frequent with dexmedetomidine (P < 0.05). Plasma norepinephrine levels increased only in the placebo group and were significantly lower for the dexmedetomidine group during the immediate postoperative period (P = 0.0002). We conclude that dexmedetomidine attenuates increases in heart rate and plasma norepinephrine concentrations during emergence from anesthesia. IMPLICATIONS: The alpha(2) agonist, dexmedetomidine, attenuates increases in heart rate and plasma norepinephrine concentrations during emergence from anesthesia in vascular surgery patients.

Adrenergic alpha-Agonists↗

PubMed2000

Magnetic resonance imaging of the normal temporal bone.

Recent advances in magnetic resonance imaging (MRI) technology has allowed the development of imaging sequences tailored to the assessment of exquisite anatomic detail of the temporal bone structures. This article describes MRI of the normal temporal bone anatomy, with emphasis on common anatomic variants and clinically relevant structures.

Ear, Inner↗

PubMed2000

Crystallization and preliminary X-ray diffraction studies of monomeric isocitrate dehydrogenase from corynrbacterium glutamicum. erratum

In the paper by Audette et al. [Acta Cryst. (1999), D55, 1584-1585] the postal code of one of the authors was printed incorrectly. The correct version is given above. Also the reaction catalyzed by isocitrate dehydrogenase was given incorrectly in the paper; the correct reaction is given below. Isocitrate + NADP(+) <--> Oxalosuccinate + NADPH. Oxalosuccinate <--> alpha-Ketoglutarate + CO(2).

Journal Article↗

PubMed2000

Functional prediction: identification of protein orthologs and paralogs.

Orthologs typically retain the same function in the course of evolution. Using beta-decarboxylating dehydrogenase family as a model, we demonstrate that orthologs can be confidently identified. The strategy is based on our recent findings that substitutions of only a few amino acid residues in these enzymes are sufficient to exchange substrate and coenzyme specificities. Hence, the few major specificity determinants can serve as reliable markers for determining orthologous or paralogous relationships. The power of this approach has been demonstrated by correcting similarity-based functional misassignment and discovering new genes and related pathways, and should be broadly applicable to other enzyme families.

3-Isopropylmalate Dehydrogenase↗

PubMed2000

The effects of childhood residence in Japan and testing language on cognitive performance in late life among Japanese American men in Hawaii.

OBJECTIVES: To examine the association of years spent in Japan during childhood with cognitive test performance in late life among Japanese American men, and to assess the influence of the language used for testing on this association. DESIGN: A cross-sectional study. SETTING/PARTICIPANTS: A total of 3734 Japanese American men, aged 71-93 years, who were first- or second-generation migrants and living on Oahu Island, Hawaii. MEASUREMENTS: The outcome variable was cognitive test performance assessed using the Cognitive Abilities Screening Instrument (CASI), which was developed for cross-cultural studies of cognitive impairment. The explanatory variable of main interest was the number of years spent in Japan during school-age childhood years (ages 6-17). The associations of CASI scores with childhood years in Japan was evaluated using a stepwise multiple linear regression model in which a total of 40 potential confounders were included as covariates. RESULTS: In the total sample, there was an inverse association between CASI scores and middle childhood years in Japan. This association remained significant after controlling for age, education, socioeconomic status, traditional Japanese food consumption, pulmonary function, apolipoprotein E4, proficiency in speaking Japanese, and other possible confounders. When data were analyzed separately for subgroups according to the language preferred at testing (English or Japanese), associations between childhood years in Japan and CASI scores were in opposite directions negative for the group tested in English and positive for the group tested in Japanese. The interaction between the testing language and childhood years in Japan was statistically significant. CONCLUSIONS: There was an inverse association between years spent in Japan during school-age years of childhood and cognitive test performance in late life. This association could not be accounted for by age, education, or other confounding factors. However, this finding was not observed in participants who preferred being tested in Japanese. To assess cognitive test performance in older people, it is of prime importance to use the most optimal language for testing, usually the subject's native language.

Adolescent↗

PubMed2000

Cloning of murine glycosyl phosphatidylinositol anchor attachment protein, GPAA1.

Glycosyl phosphatidylinositols (GPIs) are used to anchor many proteins to the cell surface membrane and are utilized in all eukaryotic cells. GPI anchoring units are attached to proteins via a transamidase reaction mediated by a GPI transamidase complex. We isolated one of the components of this complex, mGPAA1 (murine GPI anchor attachment), by the signal sequence trap method. mGPAA1 cDNA is about 2 kb in length and encodes a putative 621 amino acid protein. The mGPAA1 gene has 12 small exons and 11 small introns. mGPAA1 mRNA is ubiquitously expressed in mammalian cells, and in situ hybridization analysis revealed that it is abundant in the choroid plexus, skeletal muscle, osteoblasts of rib, and occipital bone in mouse embryos. Its expression levels and transamidation efficiency decreased with differentiation of embryonic stem cells. The 3T3 cell lines expressing antisense mGPAA1 failed to express GPI-anchored proteins on the cell surface membrane.

3T3 Cells↗

PubMed2000

Transglutaminase-mediated fibronectin multimerization in lung endothelial matrix in response to TNF-alpha.

Exposure of lung endothelial monolayers to tumor necrosis factor (TNF)-alpha causes a rearrangement of the fibrillar fibronectin (FN) extracellular matrix and an increase in protein permeability. Using calf pulmonary artery endothelial cell layers, we determined whether these changes were mediated by FN multimerization due to enhanced transglutaminase activity after TNF-alpha (200 U/ml) for 18 h. Western blot analysis indicated that TNF-alpha decreased the amount of monomeric FN detected under reducing conditions. Analysis of (125)I-FN incorporation into the extracellular matrix confirmed a twofold increase in high molecular mass (HMW) FN multimers stable under reducing conditions (P < 0.05). Enhanced formation of such HMW FN multimers was associated with increased cell surface transglutaminase activity (P < 0.05). Calf pulmonary artery endothelial cells pretreated with TNF-alpha also formed nonreducible HMW multimers of FN when layered on surfaces precoated with FN. Inhibitors of transglutaminase blocked the TNF-alpha-induced formation of nonreducible HMW multimers of FN but did not prevent either disruption of the FN matrix or the increase in monolayer permeability. Thus increased cell surface transglutaminase after TNF-alpha exposure initiates the enhanced formation of nonreducible HMW FN multimers but did not cause either the disruption of the FN matrix or the increase in endothelial monolayer permeability.

Animals↗

PubMed2000

A functional angiotensin II receptor-GFP fusion protein: evidence for agonist-dependent nuclear translocation.

We constructed an expression vector for a fusion protein [ANG II type 1a receptor-green fluorescent protein (AT(1a)R-GFP)] consisting of enhanced GFP attached to the COOH terminus of the rat AT(1a)R. Chinese hamster ovary (CHO) cells transfected with AT(1a)R-GFP demonstrated specific, high-affinity (125)I-labeled ANG II binding (IC(50) 21 nM). ANG II exposure stimulated sodium-proton exchange and cytoplasmic calcium release to a similar extent in cells transfected with AT(1a)R or AT(1a)R-GFP; these responses were desensitized by prior exposure to ANG II and were sensitive to the AT(1)R blocker losartan. ANG II-driven internalization of AT(1a)R-GFP in transfected CHO cells was demonstrated both by radioligand binding and by laser scanning confocal microscopy. Colocalization of GFP fluorescence with that of the nuclear stain TOTO-3 in confocal images was increased more than twofold after 1 h of ANG II exposure. We conclude that AT(1a)R-GFP exhibits similar pharmacological behavior to that of the native AT(1a)R. Our observations also support previous evidence for the presence of AT(1a)R in the nucleus and suggest that the density of AT(1a)R in the nucleus may be regulated by exposure to its ligand.

Angiotensin II↗

PubMed2000

Twitch transdiaphragmatic pressure depends critically on thoracoabdominal configuration.

We measured the effect of thoracoabdominal configuration on twitch transdiaphragmatic pressure (Pdi, t) in response to supramaximal, transcutaneous, bilateral phrenic nerve shocks in three thin normal men. Pdi, t was measured as a function of lung volume (VL) in the relaxation configuration, at functional residual capacity (FRC), and at the same end-tidal VL 1) during relaxation; 2) with the abdomen (Ab) expanded and the rib cage (RC) in its relaxed FRC configuration; 3) with RC expanded and Ab in its relaxed FRC configuration; and 4) in configuration 3 with an active transdiaphragmatic pressure similar to that required to produce configuration 2. In increasing VL from FRC to configuration 1, Pdi, t decreased by 3.6 cmH(2)O; to configuration 2 by 14.8 cmH(2)O; to configuration 3 by 3.7 cmH(2)O; and to configuration 4 by 2.7 cmH(2)O. We argue that changes in velocity of shortening and radius of curvature are unlikely to account for these effects and suggest that changes in diaphragmatic fiber length (L(di)) are primarily responsible. If so, equivolume displacements of Ab and RC change L(di) in a ratio of approximately 4:1. We conclude that Pdi, t is exquisitely sensitive to abdominal displacements that must be rigorously controlled if Pdi, t is to be used to assess diaphragmatic contractility.

Abdomen↗

PubMed2000

Facilitatory I wave interaction in proximal arm and lower limb muscle representations of the human motor cortex.

Transcranial magnetic stimulation (TMS) of the human motor cortex elicits direct and indirect (I) waves in the corticospinal tract. Facilitatory I wave interaction has been demonstrated with a suprathreshold first stimulus (S1) followed by a subthreshold to threshold second stimulus (S2). Intracortical inhibition (ICI) and intracortical facilitation (ICF) can be studied by another paired TMS paradigm with a subthreshold conditioning stimulus (CS) followed by a suprathreshold test stimulus. Facilitatory I wave interaction in motor representations other than the hand area and its relationship to ICI and ICF has not been studied. We studied I wave interaction, ICI and ICF in an intrinsic hand muscle (abductor pollicis brevis, APB), in a proximal arm muscle (biceps brachii, BB) and in a lower limb muscle (tibialis anterior, TA) in 11 normal subjects. I wave facilitation was studied by paired TMS at 24 interstimulus intervals (ISIs) from 0.5 to 5.1 ms. For APB and TA, facilitation occurred in three distinct peaks at ISIs of 0.9-1.7, 2. 5-3.5, and 4.1-5.1 ms. For BB, facilitation was significant for the first two peaks. The latencies of the peaks were similar among different muscles, but the magnitude of facilitation was much greater for APB and TA compared with BB. For all three muscles, changing the S2 to transcranial electrical stimulation (TES) resulted in much less facilitation of the first peak. For APB, there was significant I wave facilitation with S2 at 72% motor threshold (MT). The same stimulus used as the CS did not elicit ICF at ISI of 15 ms, suggesting that the threshold for eliciting I wave facilitation is lower than that for ICF. For BB and TA, there was no I wave facilitation with S2 at 90% of APB MT, and the same stimulus used as CS led to ICI. Thus in BB and TA the threshold for eliciting ICI is lower than that for I wave facilitation. We conclude that the circuits that mediate I wave interactions are present in the proximal arm and lower limb representations of the motor cortex. I wave facilitation occurs predominately in the cortex and may be primarily related to the monosynaptic corticomotoneuronal (CM) system. The reduced I wave facilitation for BB compared with APB and TA may be related to less extensive CM projection and involvement of other polysynaptic descending pathways. I wave facilitation, ICI, and ICF appears to be mediated by different neuronal circuits.

Adult↗

PubMed2000

Impaired growth and elevated fas receptor expression in PIGA(+) stem cells in primary paroxysmal nocturnal hemoglobinuria.

The genetic defect underlying paroxysmal nocturnal hemoglobinuria (PNH) has been shown to reside in PIGA, a gene that encodes an element required for the first step in glycophosphatidylinositol anchor assembly. Why PIGA-mutated cells are able to expand in PNH marrow, however, is as yet unclear. To address this question, we compared the growth of affected CD59(-)CD34(+) and unaffected CD59(+)CD34(+) cells from patients with that of normal CD59(+)CD34(+) cells in liquid culture. One hundred FACS-sorted cells were added per well into microtiter plates, and after 11 days at 37 degrees C the progeny were counted and were analyzed for their differentiation pattern. We found that CD59(-)CD34(+) cells from PNH patients proliferated to levels approaching those of normal cells, but that CD59(+)CD34(+) cells from the patients gave rise to 20- to 140-fold fewer cells. Prior to sorting, the patients' CD59(-) and CD59(+)CD34(+) cells were equivalent with respect to early differentiation markers, and following culture, the CD45 differentiation patterns were identical to those of control CD34(+) cells. Further analyses of the unsorted CD59(+)CD34(+) population, however, showed elevated levels of Fas receptor. Addition of agonist anti-Fas mAb to cultures reduced the CD59(+)CD34(+) cell yield by up to 78% but had a minimal effect on the CD59(-)CD34(+) cells, whereas antagonist anti-Fas mAb enhanced the yield by up to 250%. These results suggest that expansion of PIGA-mutated cells in PNH marrow is due to a growth defect in nonmutated cells, and that greater susceptibility to apoptosis is one factor involved in the growth impairment.

Antigens, CD34↗

PubMed2000

[Effect of lipoprotein lipase gene polymorphism on plasma lipid levels,BMI and subcutaneous fat distribution in simple obesity children].

OBJECTIVE: To assess the effect of Hind III DNA polymorphism in the lipoprotein lipase(LPL) gene on plasma lipid levels, body mass index(BMI) and subcutaneous fat distribution in simple obesity children. METHODS: The polymerase chain reaction(PCR) and restriction fragment length polymorphism(RFLP) techniques were used to detect the Hind III-LPL genotypes in 92 children with simple obesity. The levels of the plasma lipid, plasma lipoproteins, BMI and skinfold thickness at three measuring points(biceps, subscapular and abdominal wall) were also measured. RESULTS: The levels of TG, TC, LDL-C, Apo B, BMI, biceps and subscapular skinfold thickness with the average value of three measuring points in the obesity children with H(+) H(+)-LPL genotype were significantly higher than those in the obesity children with H(+) H(-)-LPL genotype. CONCLUSION: LPL-Hind III polymorphism may modify the levels of plasma lipid. plasma lipoproteins and BMI in children with simple obesity, and in the mean while it may affect the distribution of subcutaneous fat.

Body Mass Index↗

PubMed2000

Pregnancy outcome in women with primary renal disease.

BACKGROUND: The preconception and intraconception parameters that are relevant to outcome in women with underlying renal disease remain controversial. OBJECTIVES: To analyze the types and frequencies of short- and long-term (2 years after delivery) maternal and neonatal complications in 38 patients with primary renal disease (46 pregnancies), most of them with mild renal insufficiency. METHODS: Logistic regression models were formulated to predict successful outcome. RESULTS: Successful pregnancy outcome (live, healthy infant without severe handicap 2 years after delivery) was observed in 98% of the patients with primary renal disease. Factors found to be significantly predictive of successful outcome were absence of pre-existing hypertension, in addition to low preconception serum uric acid level. CONCLUSIONS: Most women with primary renal disease who receive proper prenatal care have a successful pregnancy outcome. Worse pregnancy outcome was observed in women with moderate or severe renal failure. Fitted logistic models may provide useful guidelines for counseling women with preexisting renal disease about their prospects for a successful pregnancy in terms of immediate and long-term maternal and neonatal outcome.

Female↗

PubMed2000

The potential for the use of mononuclear cells from human umbilical cord blood in the treatment of amyotrophic lateral sclerosis in SOD1 mice.

The SOD1 mice (transgenic B6SJL-TgN(SOD1-G93A)1GUR) have a mutation of the human transgene (CuZn superoxide dismutase gene SOD1) that has been associated with amyotrophic lateral sclerosis (ALS). In a preliminary study, we demonstrated that a megadose of human umbilical cord blood mononuclear cells given intravenously after 800 cGy of irradiation could substantially increase the life span of SOD1 mice. This report is an attempt to confirm and expand the preliminary findings. By repeating the study and raising the number of human cord blood cells from 33.2-34.0 x 10(6) to 70.2-73.3 x 10(6) there was a further significant increase in the life span of the SOD1 mice. The average life of the controls was 123.5 days while that of mice receiving the larger megadose of cells was 162 days. While all the controls were dead by 130 days, the treated group receiving 70.2-73.3 x 10(6) cells had one animal living up to 187 days and one 210 days. In order to obtain a megadose of cells, pooled blood from different donors was used and did not appear to have a negative effect, but indicated a beneficial effect on survival. The clinical significance of these findings may extend beyond the potential treatment for amyotrophic lateral sclerosis. This study confirms and extends the preliminary study whereby increasing the dose of human umbilical cord blood cells we were able to substantially further increase the survival of SOD1 mice.

Amyotrophic Lateral Sclerosis↗

PubMed2000

[Detection of anti-HIV-1/2 and HIV nucleic acid in population of non-remunerated blood donors in Shenzhen].

OBJECTIVE: To study the prevalent status of HIV-1 in population of non-remunerated blood donors in Shenzhen. METHODS: 46,095 non-remunerated blood donors were tested for anti-HIV-1/2 by ELISA. The donors of anti-HIV positive were further detected for HIV DNA from peripheral blood mononuclear cells (PMBCs) by nested-PCR and HIV RNA from plasma by RT-PCR. The partial genome of env of 2 blood donors were sequenced. RESULTS: The anti-HIV-1 was tested positive in 7 of 46 095 voluntary blood donors and the positive rate was 0.015%. In these 7 non-remunerated blood donors of anti-HIV-1 positive,7 were positive for HIV DNA in PMBCs and 5 positive for HIV RNA in plasma. The sequence analysis showed that 2 donors were infected by HIV-1 subtype E strains. CONCLUSIONS: There exists HIV-1 subtype E infection in population of non-remunerated blood donors in Shenzhen. It is essential to detect and monitor strictly the population of non-remunerated blood donors.

Adolescent↗

PubMed2000

Vitamin D receptor gene polymorphism in postmenopausal women of the Han and Uygur nationalities in China.

OBJECTIVE: Polymorphism in vitamin D receptor (VDR) gene has been reported to play a major role in variations for genetic regulation of bone mass. Its role within various ethnic populations is not clear. The purpose of this study was to determine the frequencies of VDR genotypes in the Han and Uygur nationalities in China. METHODS: We analyzed the polymorphism of Bsm I restriction enzyme by PCR-RFLP technique in 162 healthy postmenopausal women of the Han nationality and 50 healthy postmenopausal women of the Uygur nationality in China. The genotype frequencies of VDR were calculated using Hardy-Weinberg equilibrium formula. RESULTS: In the Han nationality, the bb, Bb, and BB genotype accounted for 91.36%, 8.64% and 0%, respectively. In the Uygur nationality, frequencies were 74.00%, 18.00% and 8.00%, respectively. CONCLUSION: There was a significant difference between the Han and Uygur nationalities in the frequency distribution of VDR genotype (P < 0.01). Compared with the Caucasian population in the United States, Australia and France, there was a similar value to Uygur nationality in the BB genotype. This investigation gave us further evidence on the different etiopathology of osteoporosis in various ethnic groups.

Alleles↗

PubMed2000

[Clinical study of weaning predictors in COPD patients with prolonged mechanical ventilation].

OBJECTIVE: To evaluate the combined pulmonary function test at bedside as a predicting parameter of weaning in prolonged mechanically ventilated (MV) patients with chronic obstructive pulmonary disease (COPD). METHODS: 58 patients [mean duration of MV (18.4 +/- 9.2) d] who were divided into two groups were enrolled in this study. Group I included 43 patients [male 30, female 13, mean age (65 +/- 12) y] were successful in weaning, group II included 15 patients [male 10, female 5, mean age (64 +/- 10) y] were failed. ABGs, APACHEII, pulmonary function test and respiratory mechanics were measured in both groups after 30 minutes stable spontaneous breathing. RESULTS: There were no significant difference in ABGs, APACHEII, oxygenation index (OI), dynamic compliance (Cdyn) and airway resistance (Raw) between two groups (all P values > 0.05). There were significant differences in the following parameters between two groups: vital capacity/tidal volume (VC/VT, 2.10 +/- 0.20 vs. 1.30 +/- 0.20), maximal inspiratory pressure (Pimax), (-21 +/- 4) vs. (-13 +/- 3) cm H2O, rapid shallow breath index (RSBI), f/VT, (74 +/- 30) vs. (115 +/- 20) times.min-1.L-1, all P values < 0.05. By the use of VC/VT(> 1.8), Pimax(< -18 cm H2O) and f/VT(< 105 times.min-1.L-1) as the criteria of weaning, the specificity (90%) was significantly higher than each of the above three parameters. CONCLUSION: The bedside combined pulmonary function test (VC/VT, Pimax and f/VT) was a valuable weaning predictor in prolonged mechanically ventilated COPD patients.

Aged↗

PubMed2000

[Modification of facial mask on the dead space effect in non-invasive mask ventilation].

OBJECTIVE: There were reports concerning the CO2 rebreathing during non-invasive positive pressure ventilation (NIPPV) with full face mask. It is our hypothesis that modification of the mask from one way connection to two ways connection by making a side hole in the mask makes it possible that CO2 inside the mask could be washed out by a constant flow through the mask. METHODS: A randomized self-control study on CO2 rebreathing was conducted in 7 COPD patients to compare the modified set-up with the conventional one. A BiPAP-30 ventilator and a plateau exhaustion valve (Respironics USA) were employed in the study. In the modified two ways set-up, the exhaustion valve (with distal end blocked) was connected to the side hole of the mask, so that a constant base flow could pass through the mask to the exhaustion valve. The average base flow was 0.43 LPS. The parameters were set as following: S/T mode, f: 15 BPM, pressure support level: 8 cm H2O. Three different levels of PEEP (2, 3 and 5 cm H2O) were used to investigate the PEEP level on CO2 rebreathing. Flow and CO2% were constantly recorded with computer data acquisition and analysis system (Microcal Origin). RESULTS: In conventional set-up, there was obvious CO2 rebreathing (rebreathing volume: 83.1 +/- 32.9 ml). In modified connection, the rebreathing volume was only (0.1 +/- 0.4) ml (P < 0.001). CONCLUSION: There was obvious CO2 rebreathing during full face mask NIPPV in conventional set-up. A modified two ways connection could reduce CO2 rebreathing to be near zero, which might be important in the management of hypercapnic respiratory failure with NIPPV.

Aged↗