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Biomedical subjects

C Lin

Publications and source records attributed to C Lin.

At least 163 records · Page 9Linked to original sources
PubMed1998

Regulation of flowering time by Arabidopsis photoreceptors.

The shift in plants from vegetative growth to floral development is regulated by red-far-red light receptors (phytochromes) and blue-ultraviolet A light receptors (cryptochromes). A mutation in the Arabidopsis thaliana CRY2 gene encoding a blue-light receptor apoprotein (CRY2) is allelic to the late-flowering mutant, fha. Flowering in cry2/fha mutant plants is only incompletely responsive to photoperiod. Cryptochrome 2 (cry2) is a positive regulator of the flowering-time gene CO, the expression of which is regulated by photoperiod. Analysis of flowering in cry2 and phyB mutants in response to different wavelengths of light indicated that flowering is regulated by the antagonistic actions of phyB and cry2.

Arabidopsis↗
PubMed1998

Hepatitis C virus NS3 RNA helicase domain with a bound oligonucleotide: the crystal structure provides insights into the mode of unwinding.

BACKGROUND: Hepatitis C virus (HCV) represents a major health concern as it is responsible for a significant number of hepatitis cases worldwide. Much research has focused on the replicative enzymes of HCV as possible targets for more effective therapeutic agents. HCV NS3 helicase may provide one such suitable target. Helicases are enzymes which can unwind double-stranded regions of DNA or RNA in an ATP-dependent reaction. The structures of several helicases have been published but the structural details as to how ATP binding and hydrolysis are coupled to RNA unwinding are unknown. RESULTS: The structure of the HCV NS3 RNA helicase domain complexed with a single-stranded DNA oligonucleotide has been solved to 2.2 A resolution. The protein consists of three structural domains with the oligonucleotide lying in a groove between the first two domains and the third. The first two domains have an adenylate kinase like fold, including a phosphate-binding loop in the first domain. CONCLUSIONS: HCV NS3 helicase is a member of a superfamily of helicases, termed superfamily II. Residues of NS3 helicase which are conserved among superfamily II helicases line an interdomain cleft between the first two domains. The oligonucleotide binds in an orthogonal binding site and contacts relatively few conserved residues. There are no strong sequence-specific interactions with the oligonucleotide bases.

Amino Acid Sequence↗
PubMed1998

Phylogenetic analysis of Methanobrevibacter isolated from feces of humans and other animals.

Comparative 16S rRNA gene sequence and genomic DNA reassociation analyses were used to assess the phylogenetic relationships of Methanobrevibacter fecal isolates. The 16S rRNA gene sequences of Methanobrevibacter smithii strain PS and the human fecal isolates B181 and ALI were essentially identical, and their genomic DNA reassociated at values greater than 94%. The analysis of 16S rRNA sequences of the horse, pig, cow, rat, and goose fecal isolates confirm that they are members of the genus Methanobrevibacter. They had a high degree of sequence similarity (97-98%) with the 16S rRNA gene of M. smithii, indicating that they share a common line of descent. The 16S rRNA genes of the horse and pig isolates had 99.3% sequence similarity. Sequence analysis of the 16S rRNA gene of the sheep fecal isolate showed that it formed a separate line of descent in the genus Methanobrevibacter. Genomic DNA reassociation studies indicate that the horse, pig, cow, and goose fecal isolates represent at least three new species. The horse and pig isolates were the only animal isolates that had > 70% genomic DNA reassociation and represent strains of a single species. The cow, goose, and sheep isolates had little or no genomic DNA reassociation with M. smithii or with each other. The relationship of the rat isolate to the other animal isolates was not determined. An evaluation of the relationship of 16S rRNA gene sequence similarity and genomic DNA reassociation of Methanobrevibacter and other methanogenic archaea indicated that genomic DNA reassociation studies are necessary to establish that two methanogenic organisms belong to the same species.

Animals↗
PubMed1998

Osteoporosis and coronary atherosclerosis in asymptomatic postmenopausal women.

Estrogen deficiency is a risk factor for osteoporosis and coronary artery disease. Osteoporosis can be evaluated by measuring bone mineral density (BMD). Coronary atherosclerotic burden can be evaluated by measuring coronary calcium using electron beam computed tomography (EBT) of the heart. We compared coronary calcium scores in 45 asymptomatic postmenopausal women with normal and low BMD. BMD of the lumbar spine and proximal femur was measured by dual X-ray absorptiometry (DXA), and coronary calcium was measured quantitatively by EBT. Women were divided into control, osteopenia, and osteoporosis groups based on the T score of the lumbar spine. Women were similar in age, years since menopause, height, weight, and body mass index (BMI). BMD +/- SD (g/cm2) of L1-L4 was 0.96 +/- 0.11, 0.83 +/- 0.03, and 0.73 +/- 0.05, in control, osteopenia, and osteoporosis group, respectively. The total coronary calcium score +/- SD (relative units) was 41.9 +/- 83.1, 115.1 +/- 181.9, and 221.7 +/- 355.4 for control, osteopenia, and osteoporosis group, respectively; the score was significantly higher in the osteoporosis than in the control group. This study provides initial data suggesting that women with osteoporosis may have a higher risk of developing coronary atherosclerosis.

Absorptiometry, Photon↗
PubMed1998

Evaluation of ligase chain reaction for direct detection of Mycobacterium tuberculosis in respiratory specimens.

A new automated amplification method, Ligase Chain Reaction (LCx MTB), was evaluated for direct detection of Mycobacterium tuberculosis in respiratory specimens from 208 patients and its performance was compared with culture and direct smears. Out of 226 specimens, 28 LCx MTB and 15 cultures were found positive for M. tuberculosis. After resolution of clinical history, the sensitivity of LCx MTB and culture was respectively 89.3% and 53.6% with a specificity of 98.5% and 100%. However, samples coming from untreated patients presented similar results between culture and LCx MTB (sensitivity 75% and 83.3% for culture and LCx MTB).

Automation↗
PubMed1998

Study on a fluorescence-enhanced system of 1,2,4-trihydroxyanthroquinone-Be(2+)-DNA.

Fluorescence-enhancement of 1,2,4-trihydroxyanthroquinone (THAQ)-Be2+ complex enhanced by nucleic acid was studied. Experimental results revealed that double-stranded DNA can enhance remarkably the fluorescence intensity of THAQ-Be2+, while RNA cannot. Based on these results, a fluorescence method for the selective determination of DNA in the presence of RNA was developed. Maximum fluorescence intensity was found in the pH range 3.6-4.5 with maximum excitation and emission wavelengths at 510 and 565 nm, respectively. Under optimum conditions, the calibration graph was linear over the range 0.08-18 micrograms ml-1 for double-stranded fish sperm DNA (fsDNA) with the detection limit being 2.75 x 10(-8) g ml-1. The method was applied for the determination of DNA in synthetic samples. The relative S.D. for five replicates was within 4%. In addition, the interaction mechanism of THAQ-Be2+ with DNA was also discussed.

Anthraquinones↗
PubMed1998

Specificity of electrocardiographic myocardial infarction screening criteria in patients with nonischemic cardiomyopathies.

BACKGROUND: The 32-point, 54-criteria Selvester QRS scoring system has been successfully used to estimate the size of nonacute myocardial infarction (MI). Three criteria of the system have been shown to be sensitive for the identification of nonacute MI and specific in normal control subjects. The validity of the system has not been tested in patients with cardiomyopathy of nonischemic origin. The purpose of this study was to examine the electrocardiographs (ECGs) of patients with abnormal left ventricular function but no presence of coronary disease to determine the diagnostic specificity of the MI screening criteria subset of the Selvester QRS scoring system. METHODS AND RESULTS: Six hundred ninety patients were considered. Exclusion criteria included age <10 years, cardiac transplantation, thrombolytic therapy, any angiographic evidence of coronary disease, left ventricular ejection fraction (LVEF) >60%, or history of myocardial revascularization. ECG exclusion criteria included left ventricular hypertrophy, right ventricular hypertrophy, left bundle branch block, right bundle branch block, ventricular pacing, left anterior fascicular block, left posterior fascicular block, ventricular preexcitation, and low voltage, because these confounding factors could mimic an infarct on the ECG. The 261 remaining patients were then examined for the presence of the MI screening criteria subset: (1) inferior location: Q > or =30 msec in aVF, (2) anterior location: either any Q or R< or =0.1 mV and < or =10 msec in V2, and (3) posterior location: R> or =40 msec in V1. Thirty-two of the 261 patients falsely met at least 1 of the 3 MI screening criteria, resulting in an overall specificity of 88% (vs 95% in normal control subjects, P=.0006). A specificity of 98% (n = 256) was achieved for the inferior MI screening criterion alone, whereas the anterior and posterior MI screening criteria alone achieved significantly lower specificities: 94% (n = 245) and 95% (n = 249), respectively. When the patient population was divided into LVEF <30% and LVEF > or =30%, no significant association was found between MI screening criteria and LVEF with specificities of 87% and 88%, respectively, for the 2 groups (P= .34). CONCLUSIONS: The MI screening criteria subset is relatively specific in patients with nonischemic cardiomyopathy, falsely identifying only 12% with nonacute MI. However, this specificity is lower than the 95% achieved in normal subjects. Regional accumulation of scarring caused by cardiomyopathy could result in false-positive indication of MI in the present population. Another possibility could be that some patients could have hypertrophy of the myocardium insufficient to produce positive ECG criteria for left ventricular hypertrophy or right ventricular hypertrophy but sufficient to mimic infarction.

Adult↗
PubMed1998

Burn trauma and tumor necrosis factor alpha alter calcium handling by cardiomyocytes.

It is well recognized that burn trauma induces an inflammatory cascade and the release of cytokines including tumor necrosis factor (TNF)-alpha. The negative inotropic effects of TNF-alpha on the heart are well recognized, but the cellular mechanisms remain unclear. To examine one aspect of cellular function, we exposed cardiac myocytes isolated from NZW rabbits (collagenase digestion) to either TNF-alpha (200, 400, or 1000 U/mL) or sham or burn plasma (10% by volume) for 3 to 4 h and measured calcium transient ratios in the isolated, contracting myocytes using the fluorescent indicator Fura-2-acetoxymethyl (1.2 microM); myocytes treated with media alone served as controls. Cells were placed in a perfusion chamber on the stage of an inverted Nikon microscope and superfused with buffer at 37 degrees C and stimulated at 1 Hz. A Tracor Northern Fluoroplex 1000 microspectrofluorometer and camera system, set to provide excitation of 340 and 380 nm with emission at 450-580 nm, was used to measure Ca2+ transients during systole-diastole. [Ca2+]i was reported as a fluorescence ratio (F340/F380) to minimize effects of different cell thickness and motion artifacts. After recording diastolic/systolic [Ca2+]i, cells were stimulated with isoproterenol, and [Ca2+]i was again measured. TNF-alpha produced diastolic and systolic [Ca2+]i values (1.067 +/- .023/1.301 +/- .017) that were similar to values seen after myocyte exposure to burn plasma (1.099 +/- .024/1.307 +/- .028) and significantly greater than values measured in controls (.857 +/- .017/1.077 +/- .015, p < .05). Our data confirm that burn trauma and TNF-alpha alter calcium handling by cardiomyocytes. The possible contribution of altered intracellular calcium dynamics to cardiac contractile abnormalities after burn trauma and TNF-alpha administration warrants further study.

Animals↗
PubMed1998

Pharmacological characteristics of MJ-451, a new benzopyran- derived ATP-sensitive potassium channel opener, in guinea pig isolated trachea.

In this study, we determined the pharmacological activities of MJ-451 (6-cyano-3S,4R-dihydro-2, 2-dimethyl-2H-3-hydroxy-4-[2-oxo-5S-1-hydroxmethyl)-1-pyrrolidinyl ]-1 -benzopyran) in guinea pig isolated trachea and compared its effects with those of cromakalim. MJ-451 (0.1-10 micromol/l) and cromakalim (0.01-1 micromol/l) produced concentration-dependent relaxation of guinea pig isolated trachea precontracted with carbachol (0.5 micromol/l) or histamine (1 micromol/l). MJ-451 (0.03-30 micromol/l), as well as cromakalim (0.03-30 micromol/l), caused a complete and concentration-dependent relaxation of guinea pig isolated trachea precontracted with 20 mmol/l KCl, but did not inhibit the spasmogenic effect of 80 mmol/l KCl. However, theophylline (30-3,000 micromol/l) caused a complete and concentration-dependent relaxation of guinea pig isolated trachea precontracted with either 20 or 80 mmol/l KCl. Propranolol (0.1 micromol/l) markedly antagonized the relaxant action of isoprenaline, but not that of MJ-451 in carbachol-contracted isolated trachea. 8-(p)-sulfophenyltheophylline (150 micromol/l), a selective P1 purinoceptor antagonist, had no effect against the tracheal relaxation induced by MJ-451, but markedly depressed the concentration-response curve of 5'-N-ethylcarboxamidoadenosine. Charybdotoxin (10 micromol/l), a large-conductance Ca2+-activated K+ channel blocker, failed to modify the relaxant activity of MJ-451 in carbachol-contracted isolated trachea. The ATP-sensitive K+ channel blocker, glibenclamide (0.1, 1 and 10 micromol/l) concentration-dependently antagonized the relaxant activity of MJ-451 in carbachol-contracted isolated trachea. It is concluded that MJ-451 is a selective ATP-sensitive K+ channel opener in the tracheal smooth muscle of the guinea pig.

Animals↗
PubMed1998

The effect of different fibre components on growth rate, nutrient digestibility, rate of digesta passage and hindgut fermentation in domesticated rabbits.

Trials were conducted to study the effect of dietary fibre on performance and nutrient digestibility in growing rabbits. The basal diet was supplemented with 12% cellulose, pectin, lignin, or alfalfa, in four different treatments. Twenty-four 4-week-old California male rabbits were randomly allocated into four groups and placed in individual cages. The lignin supplement severely affected both feed intake and performance, pectin second, with dietary cellulose having the least effect. Dietary lignin significantly decreased the digestibility of crude protein, gross energy and dry matter content (P < 0.05). Rabbits on the pectin supplemented diet digested dry matter, crude fibre and neutral detergent fibre (NDF) better (P < 0.05) than other treatment groups. On the other hand, rabbits in the lignin group digested crude fibre, acid detergent fibre (ADF) and NDF significantly less well than rabbits in other groups (P < 0.05). Dietary lignin also significantly decreased the caecal concentration of volatile fatty acids (VFA, P < 0.05) but did not significantly affect the molar ratios of the VFAs among treatment groups. The turnover rate of the marker, chromic oxide, in the gastrointestinal (GI) tract of rabbits was 64.94, 51.81, 44.05 and 29.59 h in the pectin, alfalfa, lignin and cellulose treatment groups, respectively. The rate of turnover in the digestive tract significantly influenced digestibility of fibre components but did not significantly influence caecal fermentation.

Animal Feed↗
PubMed1998

Treatment of posterior skull base tumors.

Surgery for posterior skull base tumors may be associated with high morbidity and mortality because of the complex anatomy, irregular bony topography, and vital neurovascular structures in this region. We experienced three benign posterior skull base tumors. These were petroclival and foramen magnum meningiomas and a jugular formen neurinoma. Three dimensional computed tomography (3 D-CT) in addition to the conventional CT, magnetic resonance imaging (MRI), and cerebral angiography were performed preoperatively. Preoperative embolizations for the tumors were also done, and intraoperative neurophysiological monitorings were performed. The tumors could be subtotally removed with no damage to the brainstem, cranial nerves, and vessels. No newly developed postoperative neurological symptoms were observed. As to the remaining tumors, gamma knife (gamma-knife) therapy was planned. 3 D-CT was very useful in the preoperative evaluation of the surgical approach, and the intraoperative neurophysiological monitoring was considered to be necessary to prevent permanent damage. gamma-knife after direct approach was recommended for the benign posterior skull base tumors.

Adult↗
PubMed1998

[Pathophysiology and surgical treatment on Relaxed Pelvic Floor Syndrome].

OBJECTIVE: To study the pathophysiology of the "Relaxed Pelvic Floor Syndrome (RPFS)" and to assess the value of the "Pelvic Cavity Fixation Operation (PCFO)" for the syndrome. METHOD: 11 patients, who were diagnosed as having RPFS, underwent standardized PCFO. All the patients were followed for a mean time of 19 months (5 - 72 months). RESULT: The main syndromes and signs included difficulty in defecation, inability to empty the rectum properly, fullness of perineum, protrusion of perineum at bearing down, back-inclining uterus, relaxation of the rectum on digital examination. The anorectal dynamics showed that the sequence pressure and rest pressure of the anal cannel were lower and the time of contraction of the anal cannel decreased than that of the normal controls. The rectum sensation was damaged slightly. Defeacography showed that there were relaxing changes in several systems in the pelvic cavity. Operatively, it was easy to see the relaxation of the supporting structure of the colon, rectum, uterus and the lower position of the peritoneal cavity. PCFO has achieved good results. Seven patients were free of symptoms completely and 4 improved. CONCLUSION: The relaxing changes of the supporting tissue of many viscus fefer to several systems are the pathophysiologic of the RPFS. "Pelvic Cavity Fixation Operation" is useful in the treatment of the syndrome.

Adult↗
PubMed1998

[Study of photoreflectance in Cd1-xMnxTe/Cd1-yMnyTe superlattices of II - VI diluted magnetic semiconductors].

The observation of photoreflectance spectra of Cd1-xMnxTe/Cd1-yMnyTe superlattices was carried out at temperature T = 80K. The samples were grown by molecular beam epitaxy (MBE) technique. The heavy-and light-hole excitonic transition structures 11H, 22H, 33H and 11L were observed and the theoretical calculations, including the strain effects, were performed. By comparison, both agree well.

English Abstract↗
PubMed1998

Pharmacokinetic and pharmacodynamic interaction between the lipoxygenase inhibitor MK-0591 and the cyclooxygenase inhibitor ibuprofen in man.

Twelve healthy male subjects participated in a double-blind, placebo-controlled, randomized, three-period, crossover study to investigate the safety, tolerability, biochemical activity and pharmacokinetics of ibuprofen, a cyclooxygenase inhibitor and MK-0591, a 5-lipoxygenase inhibitor, given as single entities and in combination. Each subject received for three consecutive 8-day periods, separated by 1 week washout, each of the following treatments: ibuprofen 600 mg three times a day with 125 mg MK-0591 twice a day, ibuprofen 600 mg three times a day with placebo for MK-0591 and MK-0591 125 mg twice a day with placebo for ibuprofen. Cyclooxygenase inhibition was measured by platelet thromboxane (TxB2) generation test, and 5-lipoxygenase inhibition was measured by urinary leukotriene E4 excretion and ex vivo LTB4 generation in calcium-ionophore-stimulated blood. TxB2 suppression on day 8 by ibuprofen was not affected by concomitant treatment with MK-0591. MK-0591 alone had no effect on TxB2 generation. Leukotriene biosynthesis was inhibited by more than 90% by MK-0591 alone and by combined treatment, while ibuprofen alone had no effect. Coadministration appears to affect the pharmacokinetics of MK-0591 (decrease of area under the plasma concentration-vs-time curve [AUC] and maximum plasma concentrations [Cmax]) and of ibuprofen (increase of AUC and half-lives of elimination (t1/2) of the (S)-enantiomer, increase of t1/2 the (R)-enantiomer). Combined treatment had no effect on creatinine clearance nor on the number and intensity of the reported adverse experiences.

Adult↗
PubMed1998

A novel Leu171Pro mutation in presenilin-1 gene in a Mexican family with early onset Alzheimer disease.

A search for mutations in exons 6, 7, 9 and 12 of the PS1 gene in four Mexican families with Early-Onset (36-40 years) Alzheimer Disease yielded the discovery in one family of a T-->C mismatch in exon 7 which correspond to nucleotide 760 of cDNA, leading to a Leu171Pro mutation. The pedigree analysis and the literature data strongly suggest an etiopathogenic relationship of the mutation with the disorder.

Adult↗
PubMed1997

The human beta globin locus introduced by YAC transfer exhibits a specific and reproducible pattern of developmental regulation in transgenic mice.

The human beta globin locus spans an 80-kb chromosomal region encompassing both the five expressed globin genes and the cis-acting elements that direct their stage-specific expression during ontogeny. Sequences proximal to the genes and in the locus control region, 60 kb upstream of the adult beta globin gene, are required for developmental regulation. Transgenic studies have shown that altering the structural organization of the locus disrupts the normal pattern of globin gene regulation. Procedures for introducing yeast artificial chromosomes (YACs) containing large genetic loci now make it possible to define the sequences required for stage-restricted gene expression in constructs that preserve the integrity of the beta globin locus. We demonstrate that independent YAC transgenic lines exhibit remarkably similar patterns of globin gene expression during development. The switch from gamma to beta globin predominant expression occurs between day 11.5 and 12.5 of gestation, with no more than twofold differences in human beta globin mRNA levels between lines. Human beta globin mRNA levels were twofold to fourfold lower than that of mouse betamaj, revealing potentially significant differences in the regulatory sequences of the two loci. These findings provide an important basis for studying regulatory elements within the beta globin locus.

Adult↗
PubMed1997

Amyloidogenic role of cytokine TGF-beta1 in transgenic mice and in Alzheimer's disease.

Deposition of amyoid-beta peptide in the central nervous system is a hallmark of Alzheimer's disease and a possible cause of neurodegeneration. The factors that initiate or promote deposition of amyloid-beta peptide are not known. The transforming growth factor TGF-beta1 plays a central role in the response of the brain to injury, and increased TGF-beta1 has been found in the central nervous system of patients with Alzheimer's disease. Here we report that TGF-beta1 induces amyloid-beta deposition in cerebral blood vessels and meninges of aged transgenic mice overexpressing this cytokine from astrocytes. Co-expression of TGF-beta1 in transgenic mice overexpressing amyloid-precursor protein, which develop Alzheimer's like pathology, accelerated the deposition of amyloid-beta peptide. More TGF-beta1 messenger RNA was present in post-mortem brain tissue of Alzheimer's patients than in controls, the levels correlating strongly with amyloid-beta deposition in the damaged cerebral blood vessels of patients with cerebral amyloid angiopathy. These results indicate that overexpression of TGF-beta1 may initiate or promote amyloidogenesis in Alzheimer's disease and in experimental models and so may be a risk factor for developing Alzheimer's disease.

Aged↗