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Biomedical subjects

J Chu

Publications and source records attributed to J Chu.

At least 37 records · Page 2Linked to original sources
PubMed2001

Stress fracture sites related to underlying bone health in athletic females.

OBJECTIVE: The study tested the hypothesis that females who sustain stress fractures of cancellous bone have decreased bone density. DESIGN: A retrospective, controlled, cross-sectional study. SETTING: The setting of the study was a tertiary care center for Women's Sports Medicine. PATIENTS: 20 female patients under the age of 40 who had suffered a stress fracture and who had a positive diagnostic study (radiograph, bone scan, or magnetic resonance imaging) were included in the study. INTERVENTIONS: Patients who had a positive diagnostic study (radiograph, bone scan, or magnetic resonance imaging) for the diagnosis of stress fracture also underwent dual energy X-ray absorptiometry (DEXA) scans. MAIN OUTCOME MEASURE: Bone density measured by the DEXA scan, as defined by the World Health Organization criteria for osteopenia (greater than one standard deviation from the standard age-matched control). RESULTS: 8 of 9 patients with cancellous stress fractures had DEXA scans indicating osteopenia while only 3 of 11 patients with stress fractures of cortical bone had a scan indicating osteopenia (p = 0.01). CONCLUSIONS: A cancellous stress fracture in a female may be a warning sign of early onset osteopenia. We recommend that young females who have documented stress fractures of cancellous bone or cortical bone (with risk factors for osteopenia) undergo bone density evaluation.

Absorptiometry, Photon↗
PubMed2001

The effect of lower-extremity position on cerebrospinal fluid pressures.

OBJECTIVE: To determine the effects of lower-extremity positioning on cerebrospinal fluid opening pressure (CSFp). The authors believed that during lumbar puncture (LP), CSFp does not meaningfully decrease when the lower extremities are extended from flexion, as is often suggested. METHODS: In a convenience sample of adult patients who clinically required LP in an urban emergency department, three sequential CSFp measurements were obtained in either sequence A (knee, hip, and neck flexion [90 degrees ], then extension, then flexion) or sequence B (extension, flexion, then extension) prior to CSF withdrawal. The neck was flexed at 30 degrees when the lower extremities were flexed, while the thoracolumbar spine was kept in the neutral position for all measurements. RESULTS: Nineteen patients were studied in each sequence. Although variable, overall within-patient changes between positions were not clinically meaningful. Mean and 95% confidence intervals (95% CIs) for the decrease in CSFp from position 1 to position 3 (same position) were 0.2 cm H(2)O (1.7%) and 0.9 to -0.6 cm H(2)O (6% to -2.7%), respectively. Changing from flexion to extension decreased pressure measurements by a mean of 0.9 cm H(2)O (2.5%) [95% CI = 2.1 to -0.1 cm H(2)O (7.6% to -2.4%)]. Changing from extension to flexion increased CSFp by a mean of 1.1 cm H(2)O (6.1%) [95% CI = 0.2 to 2.0 cm H(2)O (1.3% to 11.5%)], a statistically but not clinically meaningful change. CONCLUSIONS: Changing lower-extremity position did not meaningfully change mean CSFp. These data do not support the common suggestion that extending the lower extremities during LP meaningfully decreases CSF opening pressures.

Adolescent↗
PubMed2001

Conformal photon-beam therapy with transverse magnetic fields: a Monte Carlo study.

This work studies the idea of using strong transverse magnetic (B) fields with high-energy photon beams to enhance dose distributions for conformal radiotherapy. EGS4 Monte Carlo code is modified to incorporate charged particle transport in B fields and is used to calculate effects of B fields on dose distributions for a variety of high-energy photon beams. Two types of hypothetical B fields, curl-free linear fields and dipole fields, are used to demonstrate the idea. The major results from the calculation for the linear B fields are: (1) strong transverse B fields (> 1 T) with high longitudinal gradients (G) (> 0.5 T/cm) can produce dramatic dose enhancement as well as dose reduction in localized regions for high-energy photon beams; (2) the magnitude of the enhancement (reduction) and the geometric extension and the location of this enhancement (reduction) depend on the strength and gradient of the B field, and photon-beam energy; (3) for a given B field, the dose enhancement generally increases with photon-beam energy; (4) for a 5 T B field with infinite longitudinal gradient (solenoidal field), up to 200% of dose enhancement and 40% of dose reduction were obtained along the central axis of a 15 MV photon beam; and (5) a 60% of dose enhancement was observed over a 2 cm depth region for the 15 MV beam when B = 5 T and G = 2.5 T/cm. These results are also observed, qualitatively, in the calculation with the dipole B fields. Calculations for a variety of B fields and beam configurations show that, by employing a well-designed B field in photon-beam radiotherapy, it is possible to achieve a significant dose enhancement within the target, while obtaining a substantial dose reduction over critical structures.

Biophysical Phenomena↗
PubMed2001

Pharmacological characterization of the D1- and D2-like dopamine receptors from the brain of the leopard frog, Rana pipiens.

The pharmacological profiles of D1- and D2-like dopamine receptors were investigated for native brain receptors in the leopard frog, Rana pipiens, using direct binding assays, which characterize functional receptors rather than assess total receptor protein. We used homogenate assays of R. pipiens fore- and midbrains to determine, via saturation isotherms, that the dissociation constant, Kd, for (3)H-SCH-23390 binding to the D1-like receptors was 0.29 nM, and the maximal receptor density, Bmax, was 40 fmoles/mg protein. This compares with the more than 10-fold higher density of D1 sites in rat striatum. Specific binding for the D2-like receptors was measurable using these methods with (3)H-spiperone as the ligand. However, saturation of binding was not achieved. This contrasts with the > 400 fmoles/mg protein Bmax in rat striatum. Pharmacological profiles (rank order of potency of displacing drugs) for each receptor type were determined. We used non-radioactive SCH-23390, SKF-38393, sulpiride, and spiperone to displace (3)H-SCH-23390 and (3)H-spiperone at D1 and D2 receptors, respectively. Parallel displacement assays were performed with rat striatal controls. Results indicated that the relative rank order displacements in anuran dopamine receptors were characteristic of D1- and D2-like receptors. However, the rank orders were not identical to those in mammals. The rank order for affinity at D1-like receptors in both rats and frogs was SCH-23390 > SKF-38393 > spiperone > sulpiride. The rank order for affinity at D2-like receptors was spiperone > SCH-23390 > sulpiride > SKF-38393 in frogs, and spiperone > sulpiride > SCH-23390 > SKF-38393 in rats. SKF-38393 and spiperone had similar affinities for the 'D1' receptors in both species. SCH-23390 had a slightly lower affinity for the D1-like receptors in Rana, whereas sulpiride had a significantly lower affinity for Rana D1-like receptors compared to rat D1 receptors. In Rana D2-like receptors, spiperone and sulpiride were significantly less potent compared to rat. However, SCH-23390 and SKF-38393 were equally potent for the D2-like receptors in both species. The results indicate that amphibian brain dopamine receptors fall into two classes similar to the mammalian D1 and D2 subfamilies, but with binding characteristics slightly different from those typically described in mammals. This work represents the first pharmacological characterization of native brain dopaminergic receptors in an anuran amphibian. Because direct binding assays measure the initial aspect of the functional interaction between transmitter and receptor, these data provide an important complement to studies using cell expression systems.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed2001

Proximodistal domain specification and interactions in developing Drosophila appendages.

The morphological diversification of appendages represents a crucial aspect of animal body plan evolution. The arthropod antenna and leg are homologous appendages, thought to have arisen via duplication and divergence of an ancestral structure (Snodgrass, R. (1935) Book Principles of Insect Morphology. New York: McGraw-Hill). To gain insight into how variations between the antenna and the leg may have arisen, we have compared the epistatic relationships among three major proximodistal patterning genes, Distal-less, dachshund and homothorax, in the antenna and leg of the insect arthropod Drosophila melanogaster. We find that Drosophila appendages are subdivided into different proximodistal domains specified by specific genes, and that limb-specific interactions between genes and the functions of these genes are crucial for antenna-leg differences. In particular, in the leg, but not in the antenna, mutually antagonistic interactions exist between the proximal and medial domains, as well as between medial and distal domains. The lack of such antagonism in the antenna leads to extensive coexpression of Distal-less and homothorax, which in turn is essential for differentiation of antennal morphology. Furthermore, we report that a fundamental difference between the two appendages is the presence in the leg and absence in the antenna of a functional medial domain specified by dachshund. Our results lead us to propose that the acquisition of particular proximodistal subdomains and the evolution of their interactions has been essential for the diversification of limb morphology.

Animals↗
PubMed2001

[The genotype analysis of glucose-6-phosphate dehydrogenase deficiency in Yunnan province].

OBJECTIVE: To identify glucose-6-phosphate dehydrogenase (G6PD) gene mutations in 23 patients with G6PD deficiency and to gain further understanding of the molecular and genetic background of G6PD gene in Yunnan province, China. METHODS: The mutations located in exons 2-12 and in parts of introns of G6PD gene were analyzed by amplification refractory mutation system(ARMS), natural and mis-match primer PCR/restrict enzyme, polymerase chain reaction-single strand conformation polymorphism(PCR-SSCP ) analysis and automatic DNA sequencing. RESULTS: Among these 23 samples, 5 different point mutations in G6PD gene were identified, and they constituted 5 genotypes. There were 7 Han and 3 Dai patients with G487A mutation, 7 cases with both intron 11 T93C and C1311T mutations, 4 cases with intron 5 636 or 637 T-->del mutation, 1 case with G871A mutation, and 1 case with G487A/T93C/C1311T mutation. Two haplotypes, 93C/1311T and 93C/1311T/487A were identified in Yunnan. A strong association was observed between C1311T and the Nla III restriction site produced by intron 11 T93C. The findings of the investigators on IVS-5 636 or 637T-->del in Chinese, on G871A in mainland of China, and on G487A in the Han people of Yunnan have not been reported previously. CONCLUSION: G6PD deficiency is very heterogenous in Yunnan; G487A is one of the common mutations in that province and may be of different origins. Possibly IVS-11 T93C mutation is of non-African origin. IVS-11 T93C and C1311T might jointly result in G6PD deficiency. The above data on G6PD gene mutation types could be useful for clinical diagnosis, prevention of G6PD deficiency, and researches in the origin and migration of minorities in Yunnan or other regions.

Adolescent↗
PubMed2001

[Expression of chimeric protein of Plasmodium falciparum in yeast recombinant Pichia pastoris in cell-high-density fermentation].

The effects of cultural conditions, which were fermentation period when methanol was as sole carbon source, methanol concentration, range of pH, on the expression of the chimeric protein of Plasmodium falciparum in genetically engineered methylotrophic Pichia pastoris were investigated by shake flask experiments in this paper. The results showed: (1) fermentation period with methanol inducement is about 96 hours; (2) the optimum methanol concentration as sole carbon source is 10 g/L; (3) the range of pH is from 6.0 to 7.0. On the base of above experimental results the cell high-density fermentation had been done on the FMG-5L fermentor with multi-sensors. The results showed that the cell optical density (OD600) can reached 550 and the maximum expression level of target proteins was 780 mg/L which was 4 times higher or more than the shake flask culture's.

Animals↗
PubMed2001

[Detection and diagnosis of small peripheral lung cancers less than 15 mm in diameter].

OBJECTIVE: To assess the value of chest film, conventional CT (CCT), Spiral CT (SCT) and high resolution CT (HRCT) for detection and diagnosis of small peripheral lung cancers less than 15 mm in diameter. METHODS: Chest film, CCT, SCT and HRCT were taken in 59 cases of peripheral lung cancers less than 15 mm in diameter confirmed by operation and pathology. Their value in the diagnosis was analysed retrospectively. RESULTS: In 47% of chest films and 17% of CCT, the small lung cancer was not detected. However no tumor escaped detection by SCT. HRCT was superior for showing density and detailed image signs compared to chest film and CCT. The CT features of small peripheral lung cancers was different from those of larger peripheral lung cancers. CONCLUSION: The SCT is the best method for detection, and HRCT for diagnosis of small peripheral lung cancers less than 15 mm in diameter.

Adult↗
PubMed2001

[A novel rat aplastic anemia model induced by 5-fluorouracil combined with busulfan].

OBJECTIVE: To develop an aplastic anemia model with hematopoietic stem cell failure in rats. METHODS: Normal Wistar rats were injected i.p. with 5-fluorouracil and 5 days later p.o. by busulfan once a week for 3 times. A 5-FU alone group and a busulfan alone group were as control. The parameters tested indices were as following: incidence and mortality of aplastic anemia rats, blood picture, bone marrow nucleated cell count, CFU-GM of bone marrow cells and histology of hematopoietic organs. RESULTS: In the 5-FU plus busulfan group, the incidence of acute aplastic anemia was 82.0% (40/49 rats), the average survival time was (30.0 +/- 6.5) days. The remained 9 rats developed chronic aplastic anemia (18.0%). The total incidence of aplastic anemia was 100%, and the mortality was 98%. The blood cells count of the aplastic anemia rats was gradually reduced to a level of half the premedications and no CFU-GM was detected, and the patho-morphological examination showed that the bone marrow was replaced by fat cells, and the lymphoid tissue of spleen, thymus and lymph-nodes were remarkably atrophied without extra-medullary hematopoiesis. The control group (5-FU treated) developed a transient hematopoiesis suppression, and recovered rapidly to normal. Three of 12 rats in the busulfan treated group developed aplastic anemia. CONCLUSION: 5-FU combined with busulfan could impair the hematopoietic stem cells and resulted in an irreversible aplastic anemia in rats, making a rat aplastic anemia model with hematopoietic stem cell failure.

Anemia, Aplastic↗
PubMed2001

[The experimental study of transfected sFlt-Ig gene on K562 leukemia cell growth in nude mice].

OBJECTIVE: To observe the influence of transfected soluble vascular endothelial growth factor (VEGF) receptor (sFlt-1) gene on K562 leukemia cell growth in vivo. METHODS: (1) The binding region of VEGF receptor (Flt-1) ligand was combined with fragment of IgH stable region to construct Flt-Ig fusion gene and insert into pcDNA3 vector. (2) By using electroporation, the pcDNA3/Flt-Ig was transfected into K562 leukemia cells, and selected by G418. Flt-Ig mRNA expression was detected by RT-PCR. (3) The transfected pcDNA3/Flt-Ig and pcDNA3-Ig K562 cells were respectively transplanted into nude mice and the tumor volume was dynamically measured. RESULTS: Five subclones of K562 cells with high expression of Flt-Ig gene have been established, one of them was transplanted into 6 nude mice. The tumor volume of experimental mice was obviously smaller than that of control mice, about one half of the control group (P < 0.05). CONCLUSION: The growth of transfected pcDNA3/Flt-Ig K562 cells was significantly inhibited. It is possible that soluble Flt-Ig protein secreted from K562/Flt-Ig cells neutralized VEGF produced from tumor cells, therefore inhibited the tumor angiogenesis.

Animals↗
PubMed2001

[Effect of manganese on the ratio of micronucleus cells in mice marrow].

The ratio of micronucleus in the bone marrow cell of mice induced by manganese (Mn2+, MnCl2) through intraperitoneal injection at doses of 0, 25, 50 and 100 mg/kg respectively was investigated. The number of micronucleus cells per 1000 polychromatic erythrocyte (PCE) from breast bone marrow was counted. The results showed that micronucleus ratio in bone marrow cells were 12.0 and 16.4 per 1000 in the medium and high dosage groups, which were higher than that of control (P < 0.01). There is no distinct difference between the low dosage group and the control group (P > 0.05), but show a rising trend with the dosage of Mn2+. It indicated that the higher the dose of MnCl2, the stronger the toxic effect to the micronucleus in bone marrow cells. MnCl2 is considered having mutation to chromosome and potential heredity toxicity.

Animals↗
PubMed2001

[Reconstruction of post traumatic auricle partial defect by post-auricle flap schlepping muscle root].

OBJECTIVE: To study the method of repairing post-traumatic auricle partial defect. METHOD: 11 cases of post-traumatic auricle partial defect had been repaired by post-auricle flap schlepping muscle root in our hospital, the follow-up period from 3 months to 1 year. RESULT: It shows excellent shape. The flap necrosis hadn't been happened. CONCLUSION: Advantages of this procedure were simple to manage, texture match and good skin color. The donor scar was unconscious. It is a choice for treating post-traumatic auricle partial defect.

Adolescent↗
PubMed2001

[Studies on characteristics of kinetics and metabolic shift of genetically engineered yeast Pichia pastoris in high-density chemostat cultivation].

Kinetics and metabolic shift of DNA recombinant yeast Pichia pastoris was studied in high-density chemostat cultivation in which the glycerol was used as a limited substrate. The experimental results showed that (1) cell optical density (OD600) of Pichia pastoris was linear with its dry cell weight (DCW) and wet cell weight (WCW), and reached 100 OD600 = 128.3 g WCW/L or 100 OD600 = 22.9 g DCW/L; (2) The relationship of specific growth rate (mu) and residual concentration of glycerol is accorded with Monod Equation, to obtain mu = mumax S/(Ks + S), where mumax = 0.366 h-1, Ks = 0.1823 g/L. The maximum cell yield of glycerol substrate YG = 0.54 g/g, growth maintaining coefficient m = 0.0069 g/(g.h), The cell yield of oxygen YX/O2 = 30.96 g/moL, and the optimum theoretical dilution rate Dm = 0.341 h-1 by parameter inference; (3) With specific growth rate (mu) increasing, glycerol metablic flux shifts linearly from glycogenesis and hexosephosphate pathways to glycolysis and tricarboxylic acid cycle pathways on basis of variations of consumption rate of NH3.H2O and respiratory quotient value.

Biotechnology↗
PubMed2000

Application of microdialysis to characterize drug disposition in tumors.

Microdialysis is an in vivo sampling technique that was initially developed to measure endogenous substances in the field of neurotransmitter research. In the past decade, microdialysis has been increasingly applied to study the pharmacokinetics and drug metabolism in the blood and various tissues of both animals and humans. This paper describes the general aspects of this in vivo sampling technique followed by the survey of the recent papers regarding the application of microdialysis to characterize anticancer drug disposition in solid tumors. It can be concluded that microdialysis is a very suitable method to obtain drug concentration-time profiles in the interstitial fluid of solid tumors as well as of other variety of tissues.

Animals↗
PubMed2000

Polynesian origins: insights from the Y chromosome.

The question surrounding the colonization of Polynesia has remained controversial. Two hypotheses, one postulating Taiwan as the putative homeland and the other asserting a Melanesian origin of the Polynesian people, have received considerable attention. In this work, we present haplotype data based on the distribution of 19 biallelic polymorphisms on the Y chromosome in a sample of 551 male individuals from 36 populations living in Southeast Asia, Taiwan, Micronesia, Melanesia, and Polynesia. Surprisingly, nearly none of the Taiwanese Y haplotypes were found in Micronesia and Polynesia. Likewise, a Melanesian-specific haplotype was not found among the Polynesians. However, all of the Polynesian, Micronesian, and Taiwanese haplotypes are present in the extant Southeast Asian populations. Evidently, the Y-chromosome data do not lend support to either of the prevailing hypotheses. Rather, we postulate that Southeast Asia provided a genetic source for two independent migrations, one toward Taiwan and the other toward Polynesia through island Southeast Asia.

Biological Evolution↗
PubMed2000

Linking Notch signaling, chromatin remodeling, and T-cell leukemogenesis.

Intercellular communication that controls the developmental fate of multipotent cells is commonly mediated by the Notch family of transmembrane receptors. Specific transmembrane ligands activate Notch receptors on neighboring cells inducing the proteolytic liberation and nuclear translocation of the intracellular domain of Notch (N(IC)). Nuclear N(IC) associates with a transcriptional repressor known as C-promoter binding factor/RBP-J kappa, suppressor of hairless, or LAG-1, converting it from a repressor into an activator. Through physical interactions with chromatin remodeling enzymes and potentially with components of the transcriptional machinery, N(IC) activates target genes that mediate cell fate decisions. As Notch1 is disrupted via a chromosomal translocation in a subset of human T-cell leukemia, leading to a truncated polypeptide resembling N(IC), deregulated chromatin remodeling and transcription may fuel uncontrolled cell proliferation in this hematopoietic malignancy. This review summarizes the mechanics of Notch signaling and focuses on prospective molecular mechanisms for how constitutively active Notch might derail nuclear processes as an initiating step in T-cell leukemogenesis. J. Cell. Biochem. Suppl. 35:46-53, 2000.

Animals↗