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Biomedical subjects

C Lee

Publications and source records attributed to C Lee.

At least 127 records · Page 7Linked to original sources
PubMed2001

Cerebellar alterations induced by chronic hypoxia: an immunohistochemical study using a chick embryonic model.

A model of fetal aerogenic hypoxia was developed in which fertilized chicken eggs were half-painted with melted wax and incubated under normal conditions. The cerebellum of the hypoxic chick embryos at a later stage of development (E18-20) was analyzed immunochemically. Hypoxic insult resulted in considerable neurocytological deficits of the Purkinje cells and altered glial fibrillary acid protein (GFAP) immunoreactivity in the fetal cerebellum. Purkinje cells in the hypoxic embryos were marked by small cell size, poorly developed dendrites, low cell density, deletion and ectopia. On the other hand, enhanced GFAP immunoreactivity was found in astrocytes and Bergmann glia of the hypoxic embryos. Our results indicate that chronic hypoxia in the chick fetus can cause severe disorders of neuronal development as well as glial activation. We suggest that our hypoxic model of chick embryos could be an accessible animal model for further elucidating fetal hypoxia.

Animals↗
PubMed2001

Energy loss of fast quarks in nuclei.

We report an analysis of the nuclear dependence of the yield of Drell-Yan dimuons from the 800 GeV/c proton bombardment of 2H, C, Ca, Fe, and W targets. Employing a new formulation of the Drell-Yan process in the rest frame of the nucleus, this analysis examines the effect of initial-state energy loss and shadowing on the nuclear-dependence ratios versus the incident proton's momentum fraction and dimuon effective mass. The resulting energy loss per unit path length is -dE/dz = 2.32+/-0.52+/-0.5 GeV/fm. This is the first observation of a nonzero energy loss of partons traveling in a nuclear environment.

Journal Article↗
PubMed2001

Prenatal diagnosis and molecular cytogenetics in a case of partial trisomy 14 and monosomy 21.

We report an unbalanced translocation involving chromosomes 14 and 21 which presented as fetal ventriculomegaly at 33 weeks gestation. Second trimester ultrasound had indicated normal fetal anatomy, including normal intracranial structures. Parental karyotypes showed a paternal balanced translocation: 46,XY,t(14;21)(q12;q21). The unbalanced translocation in the fetus resulted in trisomy for 14pter-->q12 and monosomy for 21pter-->q21. Postnatal examination showed that the male infant had a cleft palate, but no cleft lip, and mild dysmorphic features. Postnatal MRI revealed bilateral and symmetric dilatation of the occipital horns, atria, and temporal horns of the lateral ventricles. Molecular cytogenetic techniques were used to delineate further the breakpoint on chromosome 14 to a site distal of the D14S1071 locus and the breakpoint on chromosome 21 to a region between D21S1918 and D21S1902. More precise definitions of chromosomal breakpoints in such clinical cases should provide more accurate prognosis for individuals with unbalanced karyotypes and assist in the identification of putative developmentally important genes.

Abnormalities, Multiple↗
PubMed2001

Development of two bacterial artificial chromosome shuttle vectors for a recombination-based cloning and regulated expression of large genes in mammalian cells.

Most conditional expression vectors designed for mammalian cells have been valuable systems for studying genes of interest by regulating their expressions. The available vectors, however, are reliable for the short-length cDNA clones and not optimal for relatively long fragments of genomic DNA or long cDNAs. Here, we report the construction of two bacterial artificial chromosome (BAC) vectors, capable of harboring large inserts and shuttling among Escherichia coli, yeast, and mammalian cells. These two vectors, pEYMT and pEYMI, contain conditional expression systems which are designed to be regulated by tetracycline and mouse interferons, respectively. To test the properties of the vectors, we cloned in both vectors the green fluorescence protein (GFP) through an in vitro ligation reaction and the 17.8-kb-long X-inactive-specific transcript (Xist) cDNA through homologous recombination in yeast. Subsequently, we characterized their regulated expression properties using real-time quantitative RT-PCR (TaqMan) and RNA-fluorescent in situ hybridization (FISH). We demonstrate that these two BAC vectors are good systems for recombination-based cloning and regulated expression of large genes in mammalian cells.

3T3 Cells↗
PubMed2001

Limitations of chromosome classification by multicolor karyotyping.

Multicolor karyotyping technologies, such as spectral karyotyping (SKY) (Schröck et al.1996; Liyanage et al. 1996) and multiplex (M-) FISH (Speicher et al. 1996), have proved to be extremely useful in prenatal, postnatal, and cancer cytogenetics. However, these technologies have inherent limitations that, in certain situations, may result in chromosomal misclassification. In this report, we present nine cases, which fall into five categories, in which multicolor karyotyping has produced erroneous interpretations. Most errors appear to have a similar mechanistic basis.

Animals↗
PubMed2001

Induction of human tumor-loaded dendritic cells.

A preferred anti-cancer vaccine would be tumor-specific, simple to rapidly construct and safe to administer. It would permit immunization against a spectrum of the tumor's distinctive antigens, without requiring their prior identification. Toward these goals, we describe a modification of standard extracorporeal photopheresis (ECP) which initiates, within a single day, both monocyte-to-dendritic cell (DC) differentiation and malignant cell apoptosis. The transition of monocytes to immature DCs was identified by the expression of cytoplasmic CD83 and membrane CD36 in the absence of membrane CD14 staining, as well as induction of membrane CD83 expression. Differentiating DCs were avidly phagocytic and engulfed apoptotic malignant T cells. Differentiating DCs were capable of stimulating significant proliferation of normal alloreactive lymphocyte responders, indicting increased expression of membrane MHC class II molecules. This approach provides a clinically practical means of developing tumor-loaded cells that have initiated the transition to DCs without the requirement of exogenous cytokines, excessive cellular manipulation or isolation. Construction of DC vaccines using this methodology can be generalized to other diseases and may offer a novel approach for improved cancer immunotherapy.

Antigens, CD↗
PubMed2001

Evidence for non-selective preservation of organic matter in sinking marine particles.

The sinking of particulate organic matter from ocean surface waters transports carbon to the ocean interior, where almost all is then recycled. The unrecycled fraction of this organic matter can become buried in ocean sediments, thus sequestering carbon and so influencing atmospheric carbon dioxide concentrations. The processes controlling the extensive biodegradation of sinking particles remain unclear, partly because of the difficulty in resolving the composition of the residual organic matter at depth with existing chromatographic techniques. Here, using solid-state 13C NMR spectroscopy, we characterize the chemical structure of organic carbon in both surface plankton and sinking particulate matter from the Pacific Ocean and the Arabian Sea. We found that minimal changes occur in bulk organic composition, despite extensive (>98%) biodegradation, and that amino-acid-like material predominates throughout the water column in both regions. The compositional similarity between phytoplankton biomass and the small remnant of organic matter reaching the ocean interior indicates that the formation of unusual biochemicals, either by chemical recombination or microbial biosynthesis, is not the main process controlling the preservation of particulate organic carbon within the water column at these two sites. We suggest instead that organic matter might be protected from degradation by the inorganic matrix of sinking particles.

Animals↗
PubMed2001

The hepatitis B virus encoded oncoprotein pX amplifies TGF-beta family signaling through direct interaction with Smad4: potential mechanism of hepatitis B virus-induced liver fibrosis.

Hepatitis B, one of the most common infectious diseases in the world, is closely associated with acute and chronic hepatitis, cirrhosis, and hepatocellular carcinoma. Many clinical investigations have revealed that hepatic fibrosis is an important component of these liver diseases caused by chronic hepatitis B. TGF-beta signaling plays an important role in the pathogenesis of fibrosis in chronic hepatitis and cirrhosis. As these diseases are associated with hepatitis B virus (HBV) infection, we examined the possibility that the HBV-encoded pX oncoprotein regulates TGF-beta signaling. We show that pX enhances transcriptional activity in response to TGF-beta, BMP-2, and activin by stabilizing the complex of Smad4 with components of the basic transcriptional machinery. Additionally, confocal microscopic studies suggest that pX facilitates and potentiates the nuclear translocation of Smads, further enhancing TGF-beta signaling. Our studies suggest a new paradigm for amplification of Smad-mediated signaling by an oncoprotein and suggest that enhanced Smad-mediated signaling may contribute to HBV-associated liver fibrosis.

3T3 Cells↗
PubMed2001

The impact of nocturnal symptoms associated with gastroesophageal reflux disease on health-related quality of life.

BACKGROUND: Two types of reflux episodes have been identified: upright or daytime and supine or nocturnal. The population-based prevalence of symptoms of nocturnal gastroesophageal reflux disease (GERD) and the impact of those symptoms on health-related quality of life (HRQL) have not been established. METHODS: A national random-sample telephone survey was conducted to estimate the prevalence of frequent GERD and nocturnal GERD-like symptoms and to assess the relationship between HRQL, GERD, and nocturnal GERD symptoms. Respondents were classified as controls, subjects with symptomatic nonnocturnal GERD, and subjects with symptomatic nocturnal GERD. The HRQL was assessed using the Medical Outcomes Study Short-Form 36 Health Survey (SF-36). RESULTS: The prevalence of frequent GERD was 14%, with an overall prevalence of nocturnal GERD of 10%. Seventy-four percent of those with frequent GERD symptoms reported nocturnal GERD symptoms. Subjects with nonnocturnal GERD had significant decrements on the SF-36 physical and mental component summary scores compared with the US general population. Subjects reporting nocturnal GERD symptoms were significantly more impaired than subjects reporting nonnocturnal GERD symptoms on both the physical component summary (38.94 vs 41. 52; P<.001) and mental component summary (46.78 vs 49.51; P<.001) and all 8 subscales of the SF-36 (P<.001). Subjects with nocturnal GERD demonstrated considerable impairment compared with the US general population and chronic disease populations. Subjects with nocturnal GERD had significantly more pain than those with hypertension and diabetes (P<.001) and similar pain compared with those with angina and congestive heart failure. CONCLUSIONS: Nocturnal symptoms are commonly experienced by individuals who report frequent GERD symptoms. In addition, HRQL is significantly impaired in those persons who report frequent GERD symptoms, and HRQL impairment is exacerbated in those who report nocturnal GERD symptoms.

Adult↗
PubMed2001

Evidence against apoptosis as a major mechanism for reproductive cell death following treatment of cell lines with anti-cancer drugs.

An increase in apoptotic cells may be observed after treatment with chemotherapy, and many authors have assumed that anti-cancer drugs kill cells by inducing apoptosis. The most relevant endpoint of cell death following treatment of tumour cells is loss of reproductive ability as measured by a colony-forming assay, since cells with limited reproductive potential cannot regenerate a tumour. We have therefore investigated the relationship between apoptosis and reproductive cell death following in vitro treatment of mammalian cell lines with anti-cancer drugs. Markers of apoptosis (DNA ladders, TUNEL assay) were evaluated at various times after treatment of Chinese Hamster Ovary (CHO) cells, human bladder cancer MGH-U1 cells, and a murine T-lymphocytic cell line (CTLL-2) with several anti-cancer drugs. These markers were found infrequently, despite the use of doses that cause loss of colony-forming ability, except in CTLL-2 cells. We also transfected and expressed the human pro-apoptotic gene bax and the anti-apoptotic gene bcl-2 in MGH-U1 cells and compared cell survival after drug treatment with that of control cells transfected with the vector alone. Expression of these genes had at most small effects to influence cell survival. We conclude that apoptotic mechanisms had at most a minor role in leading to reproductive death of MGH-U1 and CHO cells after chemotherapy. When apoptosis is observed following treatment with anti-cancer drugs it may be a secondary event which occurs in lethally-damaged cells, leading to their lysis, rather than a primary event that leads to loss of reproductive integrity.

Animals↗
PubMed2001

Reconstruction with rectus abdominis myocutaneous free flap after orbital exenteration in children.

OBJECTIVE: To present a 1-stage technique for orbital reconstruction after exenteration with the use of myocutaneous rectus abdominis free flap in children. SURGICAL TECHNIQUE: After orbital exenteration, a myocutaneous rectus abdominis free flap with long vascular pedicle is harvested from the abdomen. The flap is transferred to the orbit and the vascular pedicle is passed through an opening made in the lateral orbital wall, where it is anastomosed to superficial temporal vessels. The skin of the flap is trimmed to correspond to the eyelid defect and the incisions are closed. METHODS: After informed consent was obtained, 2 children, 3 and 8 years old, underwent orbital reconstruction with a rectus abdominis free flap after exenteration for orbital rhabdomyosarcoma and orbital osteosarcoma in the setting of retinoblastoma. RESULTS: This technique allowed easy postoperative wound care. Viability of the flap was excellent. The technique provided sufficient volume to fill the orbit, with improved aesthetic results and minimal donor site deformity. CONCLUSIONS: The postoperative care and aesthetic outcome in patients with rectus abdominis free flap after exenteration are much improved over those provided with traditional surgical techniques. This primary reconstruction is recommended for any patient requiring orbital exenteration, but particularly for pediatric patients who tolerate debridement of traditional exenteration sites poorly.

Child↗
PubMed2001

Loss of mismatch repair activity in simian virus 40 large T antigen-immortalized BPH-1 human prostatic epithelial cell line.

Simian virus 40 large T antigen (SVLTAg) has been used to immortalize cells; however, the mechanism leading to immortalization is still unclear. We hypothesize that DNA mismatch repair (MMR) activity is important during SVLTAg-induced immortalization. To test this hypothesis, we used the SVLTAg-immortalized cell line BPH-1 derived from human benign prostate epithelial cells to analyze MMR activity and the expression of MMR genes (hMLH1, hPMS1, hPMS2, hMSH2, hMSH3, and hMSH6). The results demonstrated that BPH-1 cells were deficient in repairing G:T, A:C, and G:G mispairs in bacteriophage M13mp2. Reverse-transcription polymerase chain reaction experiments indicated MMR genes (hMSH3, hMSH6, and hPMS1) were expressed at a low level in BPH-1 cells. In contrast, all six MMR genes were expressed in human benign prostate hyperplasia tissues. Downregulation of hMSH3, hMSH6, and hPMS1 genes is not a result of the hypermethylation mechanism because demethylation with 5-aza-2'-deoxycytidine did not restore expression of these genes. Although the hMLH1 gene is expressed in BPH-1 cells, western blotting and exon analyses demonstrated that hMLH1 was mutated and/or deleted in BPH-1 cells.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Robust image registration for functional magnetic resonance imaging of the brain.

Motion-related artifacts are still a major problem in data analysis of functional magnetic resonance imaging (FMRI) studies of brain activation. However, the traditional image registration algorithm is prone to inaccuracy when there are residual variations owing to counting statistics, partial volume effects or biological variation. In particular, susceptibility artifacts usually result in remarkable signal intensity variance, and they can mislead the estimation of motion parameters. In this study, Two robust estimation algorithms for the registration of FMRI images are described. The first estimation algorithm was based on the Newton method and used Tukey's biweight objective function. The second estimation algorithm was based on the Levenberg-Marquardt technique and used a skipped mean objective function. The robust M-estimators can suppress the effects of the outliers by scaling down their error magnitudes or completely rejecting outliers using a weighting function. The proposed registration methods consisted of the following steps: fast segmentation of the brain region from noisy background as a preprocessing step; pre-registration of the volume centroids to provide a good initial estimation; and two robust estimation algorithms and a voxel sampling technique to find the affine transformation parameters. The accuracy of the algorithms was within 0.5 mm in translation and within 0.5 degrees in rotation. For the FMRI data sets, the performance of the algorithms was visually compared with the AIR 2.0 software, which is a software for image registration, using colour-coded statistical mapping by the Kolmogorov-Smirov method. Experimental results showed, that the algorithms provided significant improvement in correcting motion-related artifacts and can enhance the detection of real brain activation.

Algorithms↗
PubMed2001

A new naphthoquinone from Pyrola japonica.

A new naphthoquinone, 5,8-dihydro-2,7-dimethyl-[1,4]naphthoquinone (1), which was named 5,8-dihydrochimaphilin, isolated from an ethyl acetate soluble fraction from the root of Pyrola japonica, together with chimaphilin (2). Compound 1 was transformed rapidly to 2 upon exposure to air by HPLC analysis. This fact supported that chimaphilin (2) may be an artifact from 1.

Antineoplastic Agents, Phytogenic↗
PubMed2001

Synergistic analgesic effects of intrathecal midazolam and NMDA or AMPA receptor antagonists in rats.

PURPOSE: To investigate the interaction of midazolam and N-methyl-D-aspartate (NMDA) receptor or -amino-3-hydroxy-5-methyl isoxazole-4-propionic acid (AMPA) receptor antagonist on the effects of persistent inflammatory nociceptive activation. METHODS: Male Sprague-Dawley rats were implanted with lumbar intrathecal catheters and were tested for their responses to subcutaneous formalin injection into the hindpaw. Saline, midazolam (1 to 100 microg), AP-5 (I to 30 microg), a NMDA receptor antagonist, or YM872 (0.3 to 30 microg), an AMPA receptor antagonist was injected intrathecally 10 min before formalin injection. The combinations of midazolam and AP-5 or YM872 in a constant dose ratio based on the 50% effective dose (ED50) were also tested and were analysed with an isobologram. RESULTS: Dose-dependent effects were observed with midazolam (ED50 was 1.34 microg and 1.21 microg in phase 1 and 2 of the formalin test, respectively), AP-5 (7.64 microg and 1.4 microg) and YM872 (0.24 microg and 0.21 microg). Synergistic effects in both phases were obtained when combining midazolam with AP-5 or YM872. The ED50 of midazolam decreased to 0.012 microg (phase 1) and 0.27 microg (phase 2) with AP-5 and to 0.09 microg (phase 1) and 0.35 microg (phase 2) with YM872 (P < 0.01). CONCLUSIONS: These results suggest a functional coupling of benzodiazepine-aminobutyric acid (GABA)A receptor with NMDA and AMPA receptors in acute and persistent inflammatory nociceptive mechanisms in the spinal cord.

2-Amino-5-phosphonovalerate↗
PubMed2001

Extremely low doses of tissue factor pathway inhibitor decrease mortality in a rabbit model of septic shock.

OBJECTIVE: We sought to determine the lowest dose of recombinant human tissue factor pathway inhibitor (TFPI) that can provide protection from lethality in a rabbit model of septic shock. METHODS: Sepsis was induced in New Zealand white rabbits by intraperitoneal implantation of 7.0 ml of a solution containing hemoglobin (4.8 g/dl), porcine mucin (6 g/dl), and 0.8-1.4 x 10(4) viable Escherichia coli (strain O:18 K+). Gentamicin (5 mg/kg) was administered 4 h following surgery, and this dose was repeated every 12 h for 3 days. Beginning 4 h following the induction of sepsis, animals were treated with a bolus (1 ml) plus a continuous infusion (100 ml over 24) of either TFPI (various doses) or its vehicle. Four different doses of TFPI were studied, and each experiment included a contemporaneous control group. The primary outcome parameter was survival time. Results were analyzed using the Wilcoxen log rank test. RESULTS: The average survival time for rabbits treated with the highest dose of TFPI tested (50 microg/kg bolus and 0.5 microg/kg per minute infusion) was 118 h, as compared to 81 h in vehicle-treated controls). The average survival time for septic rabbits treated with a much lower dose of TFPI (100 ng/kg bolus and 1.0 ng/kg per minute infusion) was 119 h as compared to 57 h in surviving vehicle-treated controls. Treatment with an even lower dose of TFPI (10 ng/kg bolus and 0.1 ng/kg per minute infusion) still produced a marginally significant prolongation of average survival time (80 h) relative to contemporaneously studied controls (47 h). When the dose of TFPI was decreased still further (1.0 ng/kg bolus and 0.01 ng/kg per minute infusion), average survival times were not significantly different between TFPI-treated and vehicle-treated rabbits (77 and 51 h, respectively). CONCLUSIONS: Delayed infusion with remarkably low doses of recombinant human TFPI prolongs survival in a rabbit model of antibiotic-treated Gram-negative bacterial sepsis. In planning human trials of TFPI as an adjuvant treatment for sepsis it may be reasonable to use much lower doses of the agent than were heretofore contemplated.

Animals↗
PubMed2001

Genomic structure, functional comparison, and tissue distribution of mouse Cd59a and Cd59b.

CD59 is a crucial complement regulatory protein that inhibits the terminal step of the complement activation cascade by interfering with the binding of C9 to C5b-8, thus preventing the formation of the membrane attack complex (MAC). We recently reported that the mouse genome contains two Cd59 genes, while the human and rat genomes each contain only one Cd59 gene (Qian et al. 2000). Here, we describe the genomic structure, comparative activity, and tissue distribution of these two mouse genes, designated Cd59a and Cd59b. The mouse Cd59 genes encompass a total of 45.6 kb with each gene having four exons. Cd59a spans 19 kb, and Cd59b spans 15 kb, with approximately 11.6 kb of genomic DNA separating the two genes. The overall sequence similarity between Cd59a and Cd59b is approximately 60%. The sequence similarity between exon 2, exon 3, and exon 4 and the respective flanking regions between the two genes is over 85%, but exon 1 and its flanking regions are totally different. Comparative studies of the activity of both genes as inhibitors of MAC formation revealed that Cd59b has a specific activity that is six times higher than that of Cd59a. Using polyclonal antibodies specific to either Cd59a or Cd59b, we showed that Cd59a and Cd59b are both widely expressed in the kidneys, brain, lungs, spleen, and testis, as well as in the blood vessels of most mouse tissues. Interestingly, testicular Cd59a appeared to be expressed exclusively in spermatids, whereas Cd59b was expressed in more mature sperm cells. These results suggest that even though Cd59a and Cd59b are expressed in multiple tissues, they may play some different roles, particularly in reproduction.

Animals↗