Biomedical subjects

C Lee

Publications and source records attributed to C Lee.

At least 361 records · Page 20Linked to original sources

PubMed1998

A global survey of haplotype frequencies and linkage disequilibrium at the DRD2 locus.

A four-site haplotype system at the dopamine D2 receptor locus (DRD2) has been studied in a global sample of 28 distinct populations. The haplotype system spans about 25 kb, encompassing the coding region of the gene. The four individual markers include three TaqI restriction site polymorphisms (RSPs) -- TaqI "A", "B", and "D" sites -- and one dinucleotide short tandem repeat polymorphism (STRP). All four of the marker systems are polymorphic in all regions of the world and in most individual populations. The haplotype system shows the highest average heterozygosity in Africa, a slightly lower average heterozygosity in Europe, and the lowest average heterozygosities in East Asia and the Americas. Across all populations, 20 of the 48 possible haplotypes reached a frequency of at least 5% in at least one population sample. However, no single population had more than six haplotypes reaching that frequency. In general, African populations had more haplotypes present in each population and more haplotypes occurring at a frequency of at least 5% in that population. Permutation tests for significance of overall disequilibrium (all sites considered simultaneously) were highly significant (P<0.001) in all 28 populations. Except for three African samples, the pairwise disequilibrium between the outermost RSP markers, TaqI "B" and "A", was highly significant with D' values greater than 0.8; in two of those exceptions the RSP marker was not polymorphic. Except for those same two African populations, the 16-repeat allele at the STRP also showed highly significant disequilibrium with the TaqI "B" site in all populations, with D' values usually greater than 0.7. Only four haplotypes account for more than 70% of all chromosomes in virtually all non-African populations, and two of those haplotypes account for more than 70% of all chromosomes in most East Asian and Amerindian populations. A new measure of the amount of overall disequilibrium shows least disequilibrium in African populations, somewhat more in European populations, and the greatest amount in East Asian and Amerindian populations. This pattern seems best explained by random genetic drift with low levels of recombination, a low mutation rate at the STRP, and essentially no recurrent mutation at the RSP sites, all in conjunction with an "Out of Africa" model for recent human evolution.

Alleles↗

PubMed1998

Analytical evaluation of the testosterone assay on the Bayer Immuno 1 system.

OBJECTIVES: To evaluate the analytical performance of the testosterone assay performed on the Bayer immuno 1 system from Bayer Corporation. DESIGN AND METHODS: The precision was measured using three Bayer TESTpoint Ligand controls, three Medical Decision Pools and the Bayer SETpoint Testosterone calibrators. The linearity was verified by diluting two serum samples containing high testosterone concentrations with the zero calibrator and the minimum detectable concentration determined by repetitive analysis of the zero calibrator. The assay was correlated with the Diagnostic Products Corporation (DPC) Total Testosterone assay using 342 serum samples. The reference values were determined using serum samples from 75 women and 60 men. RESULTS: The assay showed within-run coefficients of variation (CVs) varying from 1.1-8.4% and between-day CVs from 1.5-4.9% for testosterone concentrations varying from 1.77 to 66.96 nmol/L. The minimum detectable concentration was estimated at 0.11 nmol/L. The assay linearity proved excellent. A good correlation between the Bayer Immuno 1 and the DPC assays was observed with different categories of serum samples (Immuno 1 = 1.11 x DPC-0.32, r = 0.989, Sy[symbol: see text]x = 2.07 nmol/L). The reference values were estimated at 0.3-3.2 nmol/L for females and 9.3-35.6 nmol/L for males. CONCLUSIONS: The Bayer Immuno 1 Testosterone assay demonstrates the analytical characteristics required for its utilization in the clinical laboratory.

Adult↗

PubMed1998

Interference of 6 beta-hydroxycortisol in the quantitation of urinary free cortisol by immunoassay and its elimination by solid phase extraction.

OBJECTIVE: To study the cross-reactivity of 6 beta-hydroxycortisol (6 beta-OHF) with anticortisol antibodies and subsequent interference with urinary free cortisol (UFC) quantitation in commercial immunoassay kits. A solid-phase-extraction (SPE) technique was evaluated for removal of 6 beta-OHF from the specimen. METHODS: Interference by 6 beta-OHF was studied in three enzyme immunoassay and three radioimmunoassay kits. Interference was assessed by the multiple regression equation derived from a 4 x 4 matrix composed of four levels of cortisol and four levels of 6 beta-OHF. Sep-Pak Plus C18 cartridges were used to remove 6 beta-OHF from the specimens, and optimum conditions for fractionating 6 beta-OHF from cortisol were determined by eluting the cartridge with a stepwise increment in methanol concentration. HPLC was used to monitor cortisol and 6 beta-OHF in the sample and cartridge eluates. RESULTS: Cross-reactivity of 6 beta-OHF with anticortisol antibodies was variable and depended on the cortisol kit used with a range from 0.1 to 10%. Multiple regression analysis indicated that 6 beta-OHF interfered positively with the cortisol assay regardless of cortisol concentrations. Extraction of UFC by methylene chloride as recommended by some immunoassay kits yielded a significant constant error to the UFC results which was nearly proportional to the added levels of 6 beta-OHF. SPE of samples completely removed 6 beta-OHF from the specimen when a 40% methanol elution step was included. Consequently, specimens processed in this manner did not show interference in UFC measurements even in samples spiked with 2.38 mumol/L of 6 beta-OHF. CONCLUSIONS: Elevated urinary 6 beta-OHF may be a significant source of interference in UFC immunoassays. SPE of samples prior to analysis would be a simple and inexpensive means for removing 6 beta-OHF from urine specimens, therefore, increasing accuracy and precision in UFC measurements by immunoassay.

Chemical Fractionation↗

PubMed1998

Unsupervised connectivity-based thresholding segmentation of midsagittal brain MR images.

In this paper, we propose an algorithm for automated segmentation of midsagittal brain MR images. First, we apply thresholding to obtain binary images. From the binary images, we locate some landmarks. Based on the landmarks and anatomical information, we preprocess the binary images, which substantially simplifies the subsequent operations. To separate regions what are incorrectly merged after this initial segmentation, a new connectivity-based threshold algorithm is proposed. Assuming that some prior information about the general shape and location of objects is available, the algorithm finds a boundary between two regions using the path connection algorithm and changing the threshold adaptively. In order to test the robustness of the proposed algorithm we applied the algorithm to 120 midsagittal brain images and obtained satisfactory results.

Algorithms↗

PubMed1998

Low total body bone mineral content and high bone resorption in Korean winter-born versus summer-born newborn infants.

Seasonal differences in newborn total body bone mineral content (TBBMC) have not been studied, particularly in relation to alterations in vitamin D status in winter. In vitamin D deficiency bone resorption may be high and bone mineralization low. Bone resorption may be assessed by serum cross-linked carboxyterminal telopeptide of type I collagen (ICTP) measures. Because vitamin D supplements throughout pregnancy are uncommon in Korea, we hypothesized that in Korean winter newborns, TBBMC is low and serum ICTP high from high bone resorption and low 25-hydroxyvitamin D (25-OHD) compared with those in summer newborns. Seventy-one Korean term infants were studied prospectively in summer (July through September, n = 37) versus winter (January through March, n = 34); TBBMC was measured before 3 days of age by dual-energy x-ray absorptiometry. Significant seasonal differences were found: winter newborns had 6% lower TBBMC (least squares means +/- SD; 86.7 +/- 7.7 gm vs 93.9 +/- 7.8 gm, p = 0.0002), lower cord serum 25-OHD (10.7 +/- 8 nm vs 30 +/- 15 nm, p = 0.0001) and 1,25-dihydroxyvitamin D, and higher ICTP (96.4 +/- 20.3 microg/L vs 74.8 +/- 24 microg/L, p = 0.0002) and calcium than summer newborns. TBBMC correlated with serum 25-OHD (r = 0.243, p = 0.047) and inversely with ICTP (r = -0.333, p = 0.008). We suggest that in Korea low maternal vitamin D status in winter results in marked reduction in newborn TBBMC.

Absorptiometry, Photon↗

PubMed1998

Synergistic action of steroids and spermatocele fluid on in vitro proliferation of prostate stroma.

PURPOSE: Our goal is to understand human prostate growth phenomena potentially important to BPH development and growth. The objective of the present study is to characterize in vitro prostate stromal proliferative factors in testis epididymal secretions. MATERIALS AND METHODS: Human spermatocele fluids were used as a source of testicular epididymal plasma (STEP). Primary cultures of human prostate stromal cells were routinely grown in RPMI-1640 with 10% fetal bovine serum. During a 6-day experimental period, cells were cultured in RPMI-1640 in the absence of serum but supplemented with ITS. Whole STEP, ether stripped STEP, or heparin affinity column treated STEP was included in the culture medium with and without the addition of testosterone (T), dihydrotestosterone (DHT), or estradiol (E). Results of these treatments were assessed by cell counts. Antibodies against smooth muscle myosin heavy chain, smooth muscle alpha actin, and prolyl-4-hydroxylase were utilized in immunocytochemical characterization of cultured cells. RESULTS: Whole STEP stimulated prostatic stromal cells derived from prostates of 15, 45, 70 and 72-year-old men. Treatment of STEP by ether stripping or heparin affinity column exposure did not result in a significant reduction in cell counts. With the exception of the 15-year-old specimen, addition of T or DHT to ether stripped STEP resulted in a significant increase in cell counts over that of ether stripped STEP treatment alone. Preliminary immunocytochemical evaluation indicated the presence of variable mixture of fibroblasts, myofibroblasts, and smooth muscle cells in these cultures. CONCLUSIONS: These in vitro observations indicate that testis epididymal secretions contain androgen/STEP synergistic and androgen independent STEP factors promoting prostate stromal growth. These factors are not heparin binding. These observations are consistent with the concept that, in addition to the production of steroids, the testis produces non-androgenic factors that act in concert with, as well as independently of, androgen to stimulate prostatic growth.

Adolescent↗

PubMed1998

Neuromuscular blocking N,N'-polymethylene bistropanium, bis 3alpha-hydroxytropanium and bis 3-oxotropanium compounds.

To explore the role of ester groups in the neuromuscular blocking (NMB) property of various quaternary ammonium tropinesters, we have synthesized and pharmacologically evaluated twenty bisquaternary ammonium derivatives where two tropane (I), 3alpha-hydroxytropane (II), or 3-oxotropane (III) moieties were connected on their nitrogen atoms with a polymethylene chain of C3-C12 length. The rank order of potency of these agents in the rat (evoked EMG responses of the ant. tibial muscle) was: I, II, and III. Most potent were the longer chain (e.g. C10-C12) compounds of series I, yet they were inferior to bisquaternary ammonium tropinester derivatives (e.g. N,N'-polymethylene bisquaternary tropinesters, or bisquaternary derivatives of dicarboxylic acid tropinesters). Although some of the agents (series I and II) showed a rapid onset and short duration of action-profile, they also exhibited cardiovascular side effects (e.g. cardiac vagal block and blood pressure changes). In the design of new NMB agents of rapid onset and short duration of action the presence of different ester groups in addition to an azabicyclo ring system (e.g. tropane), seems to be essential.

Animals↗

PubMed1998

Pediatric Wegener's granulomatosis complicated by central nervous system vasculitis.

An unusual case of central nervous system vasculitis in pediatric Wegener's granulomatosis, a rare disorder that infrequently presents during childhood, is reported. A 13-year-old girl with Wegener's granulomatosis, whose initial presentation resembled Henoch-Schonlein purpura, developed recurring seizures. MRI of the brain demonstrated multiple areas of increased signal in the occipital, parietal, and frontal lobes, consistent with central nervous system vasculitis. Although both peripheral and cranial neuropathies have been reported in patients with Wegener's granulomatosis, cerebral vasculitis is unusual, particularly in childhood. This case emphasizes the need to consider Wegener's granulomatosis in the differential diagnosis of both unexplained seizures and central nervous system vasculitis in children with systemic illness.

Adolescent↗

PubMed1998

The Drosophila CLOCK protein undergoes daily rhythms in abundance, phosphorylation, and interactions with the PER-TIM complex.

We report the in vivo characterization of the Drosophila CLOCK protein (dCLOCK), a transcription factor that is required for the expression of the circadian clock genes period (per) and timeless (tim). dCLOCK undergoes circadian fluctuations in abundance, is phosphorylated throughout a daily cycle, and interacts with PER, TIM, and/or the PER-TIM complex during the night but not during most of the day. Our results suggest that PER and TIM participate in transcriptional autoinhibition by physically interacting with dCLOCK or a dCLOCK-containing complex. Nevertheless, in the absence of PER or TIM, the levels of dCLOCK are constitutively low, indicating that PER and TIM also act as positive elements in the feedback loop by stimulating the production of dCLOCK.

Animals↗

PubMed1998

Leptin activates hypothalamic CART neurons projecting to the spinal cord.

The adipocyte-derived hormone leptin decreases body weight in part by activating the sympathetic nervous system, resulting in increased thermogenesis and energy expenditure. We investigated hypothalamic pathways underlying leptin's effects on stimulating the sympathetic nervous system. We found that leptin activates neurons in the retrochiasmatic area (RCA) and lateral arcuate nucleus (Arc) that innervate the thoracic spinal cord and also contain cocaine- and amphetamine-regulated transcript (CART). We also found that most CART-containing neurons in the RCA and Arc of the hypothalamus also contain proopiomelanocortin (POMC) mRNA. The finding that leptin activates CART/POMC neurons innervating sympathetic preganglionic neurons in the thoracic spinal cord suggests that this pathway may contribute to the increased thermogenesis and energy expenditure and decreased body weight observed following leptin administration.

Animals↗

PubMed1998

Camptothecin-20-PEG ester transport forms: the effect of spacer groups on antitumor activity.

An improved synthesis of the hindered PEG-camptothecin diester transport form has been achieved using the Mukaiyama reagent. We have also assessed the effect of changing the electronic configuration of the (d-position of PEG-camptothecin transport forms on the rates of hydrolysis of the pro-moiety, and attempted to correlate these differences to efficacy in two animal models. In addition to the simple substitution of N for O, other synthetic modifications of these atoms were accomplished by employing heterobifunctional linker groups. The half lives by disappearance (rates of hydrolysis) of the transport forms in buffer and rat plasma were determined. It was established that anchimeric assistance to hydrolytic breakdown of the pro-moiety occurs in a predictable manner for some of these compounds. Results for the new derivatives in a P388 murine leukemic model and HT-29 human colorectal xenograft study are also presented. The use of a glycine linker group was found to provide similar efficacy in rodent models to that of simple camptothecin 20-PEG ester, and displayed enhanced pharmacokinetics.

Animals↗

PubMed1998

Epidermal growth factor receptor activation in androgen-independent but not androgen-stimulated growth of human prostatic carcinoma cells.

These studies were undertaken to assess the relative expression and autocrine activation of the epidermal growth factor receptor (EGFR) in normal and transformed prostatic epithelial cells and to determine whether EGFR activation plays a functional role in androgen-stimulated growth of prostate cancer cells in vitro. EGFR expression was determined by Western blot analysis and ELISA immunoassays. Immunoprecipitation of radiophosphorylated EGFR and evaluation of tyrosine phosphorylation was used to assess EGFR activation. The human androgen-independent prostate cancer cell lines PC3 and DU145 exhibited higher levels of EGFR expression and autocrine phosphorylation than normal human prostatic epithelial cells or the human androgen-responsive prostate cancer cell line LNCaP. PC3 and DU145 cells also showed higher levels of autonomous growth under serum-free defined conditions. Normal prostatic epithelial cells expressed EGFR but did not exhibit detectable levels of EGFR phosphorylation when cultured in the absence of exogenous EGF. Addition of EGF stimulated EGFR phosphorylation and induced proliferation of normal cells. LNCaP cells exhibited autocrine phosphorylation of EGFR but did not undergo significant proliferation when cultured in the absence of exogenous growth factors. A biphasic growth curve was observed when LNCaP cells were cultured with dihydrotestosterone (DHT). Maximum proliferation occurred at 1 nM DHT with regression of the growth response at DHT concentrations greater than 1 nM. However, neither EGFR expression nor phosphorylation was altered in LNCaP cells after androgen stimulation. In addition, DHT-stimulated growth of LNCaP cells was not inhibited by anti-EGFR. These studies show that autocrine activation of EGFR is a common feature of prostatic carcinoma cells in contrast to normal epithelial cells. However, EGFR activation does not appear to play a functional role in androgen-stimulated growth of LNCaP cells in vitro.

Adult↗

PubMed1998

Phenotypic and functional reconstitution of peripheral blood lymphocytes following T cell-depleted bone marrow transplantation from partially mismatched related donors.

Myeloablative chemotherapy followed by transplantation of a T cell-depleted bone marrow graft from a partially mismatched related donor provides a potentially curative option for patients with leukemia and other disorders of hematopoiesis, although the patient is faced with a period of sustained immunodeficiency as well as pharmacologic immunosuppression as a result of prophylaxis against graft-versus-host disease. Thirty patients who received one to three antigen T cell-depleted mismatched grafts were evaluated for immune reconstitution. The percentage and numbers of cells expressing lymphocyte subset antigens were determined by flow cytometry at 14, 28, 60, 100, 180, 270 and 365 days post-BMT and at 6 month intervals thereafter. Lymphocyte reconstitution was characterized by the early appearance of natural killer cells and a low percentage of both T and B cells. During the first year after BMT, the number of NK cells remained constant while T and B cells gradually returned to normal numbers and proportions. Response to the lymphocyte mitogen phytohemagglutinin returned to normal over the course of 2 years, while the response to concanavalin A was slightly depressed and the response to pokeweed mitogen became supranormal at about 1.5 years and continued to increase. These data suggest the need for long-term immunophenotypic monitoring as well as prolonged infection surveillance and prophylaxis.

B-Lymphocytes↗

PubMed1998

Does withholding gonadotrophin administration prevent severe ovarian hyperstimulation syndrome?

Withholding gonadotrophin administration (coasting) may prevent severe ovarian hyperstimulation syndrome (OHSS). To ascertain the effectiveness of this protection a cohort of 252 consecutive in-vitro fertilization (IVF) or IVF with intracytoplasmic sperm injection (ICSI) cycles was studied. Twenty women with exaggerated response were treated with coasting. Despite coasting, four patients developed severe OHSS requiring hospitalization. Two of these four patients also required paracentesis. Multiple regression analysis in coasting cycles revealed severe OHSS was related to youth, number of oocytes retrieved and serum oestradiol prior to human chorionic gonadotrophin (HCG). Risk of developing severe OHSS was multifactorial and not necessarily prevented by withholding gonadotrophin.

Adult↗

PubMed1998

Expression of Tcf-1 mRNA and surface TCR-CD3 complexes are reduced during apoptosis of T cells.

When a T cell hybridoma, 70.7, was treated with a Ca2+ ionophore (A23187), apoptotic cell death was induced. Interestingly, we observed that the expression of Tcf-1, a T cell-specific transcription factor, mRNA was reduced by approximately 5-fold in the A23187-treated apoptotic cells compared to an ethanol-treated control. The hybridoma cells, however, did not display such a reduced expression of Tcf-1 mRNA upon treatment with buthionine sulfoxide, which is known to induce a necrosis-like cell death. When another T cell hybridoma, KMIs-8.3.5, was treated with A23187 and phorbol myristate acetate, which leads to activation-induced apoptosis, Tcf-1 expression was again greatly reduced. However, a mutant line (KCIT1-8.5) derived from KMIs-8.3.5, which produces IL-2 upon activation and is resistant to apoptosis, did not show such reduction in Tcf-1 expression. We also showed that the reduced expression level of CD3epsilon mRNA and surface TCR-CD3 complex in apoptotic T cells is caused by the reduced expression of Tcf-1. When 70.7 cells were transfected with a plasmid DNA pSVtcf-1, in which Tcf-1 gene expression is driven by the SV40 promoter, such reduction of the Tcf-1 mRNA and the surface expression of the TCR-CD3 complex were not observed upon apoptosis induction. Our results suggest that the reduced expression of Tcf-1 is specific for the apoptotic, but not for the activating, process of T cells and is also responsible for the reduced surface expression of the TCR-CD3 in apoptotic T cells.

Animals↗

PubMed1998

Endoscopic harvest of the gracilis muscle flap.

Endoscopic technique is becoming increasing prevalent in plastic surgery and is being explored for use in tissue harvest for microneurovascular transplantation. To advance the art truly, endoscopic technique must provide similar success and complication rates, operative time, and ease of performance as the traditional "open" surgical harvest. We report the successful microvascular transplantation in 6 patients of gracilis muscles harvested with endoscopic guidance. Dissection of the primary pedicle was done through a small proximal incision, and subsequent dissection was accomplished with an endoscope through the primary incision and a small distal incision. This method provides excellent success of transfer and decreased morbidity compared with the open technique. Specifically, the resulting scar from the endoscopic technique is considerably smaller, with just a 5-cm proximal and a 1.5-cm distal scar. The technique is accomplished with standard endoscopic equipment and is learned rapidly. We believe the improved aesthetic outcome makes endoscopic gracilis harvest a preferred technique.

Adult↗

PubMed1998

Magnetic resonance features of the enigmatic oligodendroglioma.

RATIONALE AND OBJECTIVES: The authors characterize magnetic resonance (MR) features of oligodendroglioma that permit diagnosis. These features may be used to guide MR stereotactic biopsies. METHODS: Fifteen patients with mixed oligodendroglioma and four with pure oligodendroglioma were studied on a 1.5-tesla MR unit with contrast and also by computed tomography (CT). All patients had their diagnosis confirmed by light and electron microscopy, and by immunohistochemical staining. RESULTS: The most characteristic finding was a honeycomb tumor matrix (4 of 19) in oligodendroglioma. The most common finding was an amorphous pattern (12 of 19) and the least common was a large cystic pattern (3 of 19). Contrast enhancement most commonly was minimal and dot-like or lacy in appearance (11 of 19), or absent (5 of 19). Calcification was present in the majority (11 of 19). CONCLUSIONS: The honeycomb and stippled amorphous patterns reflect the cytoarchitecture of oligodendroglioma and were the most characteristic MR features. The amorphous pattern was the most commonly encountered pattern. There was a wider range of imaging findings on MR compared with CT; the flocculent calcification on CT was typical, but it was not always detected on MR. Including these characteristic areas that appear along the path of the stereotactic biopsy may ensure a correct diagnosis of oligodendroglioma because it most often is seen with another tumor, usually of the astrocytic family. Identifying the oligodendrogliomatous portion of the tumor will influence the therapy. No differences could be found in the MR appearance or biologic behavior of pure versus mixed oligodendrogliomas.

Adolescent↗

PubMed1998

Magnetic resonance imaging in a spinal abscess model. Preliminary report.

RATIONAL AND OBJECTIVES: Magnetic resonance (MR) scan technique and lesion detectability were evaluated using a newly developed spinal abscess model in the New Zealand White rabbit. METHODS: To create the lesion, an epidural needle was inserted under fluoroscopic guidance in the lumbar region and advanced to penetrate the ligamentum flavum. Next, polyethylene tubing was fed through the needle into the epidural space. A mixed suspension of Staphylococcus aureus (Cowan I) and blue polystyrene microspheres then was injected. Lesions were evaluated by MR imaging in four animals at multiple time points (3, 6, and 9 days). Imaging was performed at 1.5 tesla using a surface coil. Precontrast T2-and T1-weighted scans were first obtained. The T1-weighted scans were acquired both with and without fat saturation, and were repeated after intravenous contrast administration. The contrast agent used was gadoteridol (gadolinium HP-DO3A or ProHance) at a dose of 0.3 mmol/kg. RESULTS: On prospective film review, postcontrast scans proved superior for lesion detection. A spinal abscess could be identified postcontrast in all cases, irrespective of the use of fat saturation. The next best imaging technique for lesion detection was the T2-weighted scan, with 5 of 8 lesions noted thereon. Visualization of lesion margins proved to be a primary factor in prospective lesion identification. Region of interest image analysis demonstrated the postcontrast scans to be superior to all precontrast scan techniques for conspicuity of the interface between the abscess and the compressed spinal cord, with these results statistically significant. The lesions were characterized histologically by infiltrates of heterophils into the meninges and outer spinal cord with accompanying mild hemorrhage, fibrin exudation, and bacterial colonies. The lesions in three animals were confirmed to be in the epidural space, with the lesion in one animal in the subdural space. CONCLUSIONS: The current animal model was developed to study spine infection and, specifically, imaging characteristics and lesion detectability on MR. With the increased use of epidural catheters for pain management and the large number of acquired immunodeficiency syndrome cases, epidural infection is becoming an increasingly important clinical problem. Imaging technique, in particular the use of intravenous contrast, is critical for lesion detection and evaluation.

Abscess↗