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C S Chen

Publications and source records attributed to C S Chen.

At least 109 records · Page 6Linked to original sources
PubMed1997

Hydroxyl radical-induced decline in motility and increase in lipid peroxidation and DNA modification in human sperm.

We employed the xanthine-xanthine oxidase system to produce H2O2 or simply used commercially available H2O2 solution to investigate the effects of exogenous hydroxyl radicals on the motility characteristics and on lipid peroxidation and DNA modification of human sperm. The functional parameters of sperm motility declined concomitantly upon incubation of sperm with hydroxyl radicals. After incubation of freshly ejaculated human sperm with 0.23 mM H2O2 in the presence of 1.8 mM ADP and 2.7 mM FeSO4 for 1 hr at 37 degrees C, 90% reduction of motility was observed. Effect of hydroxyl radicals on sperm motility was dependent on the concentrations of FeSO4 and H2O2, respectively. The remaining motility of sperm after 1 hr incubation showed negative linear correlation with FeSO4 concentration. The response of sperm motility to FeSO4 was also dependent on the concentration of H2O2. Except for the amplitude of lateral head displacement, functional parameters of sperm declined with the increase of H2O2 concentration. Moreover, we found that lipid peroxidation measured as malondialdehyde (MDA) and accumulation of modified DNA indicated by 8-hydroxy-2'-deoxyguanosine (8-OH-dG) in human sperm were significantly accelerated by exogenous hydroxyl radicals. The contents of lipid peroxides and 8-OH-dG in the spermatozoa were increased from 24.6 +/- 2.4 nmol MDA/1 x 10(7) sperm and 0.17 +/- 0.02% in the untreated group to 30.6 +/- 1.2 nmol MDA/1 x 10(7) sperm and 1.9 +/- 0.47%, respectively, in the sperm treated at 37 degrees C for 1 hr with 2.03 mM H2O2, 1.8 mM ADP and 4.5 mM FeSO4. Taken together, these results suggest that the detrimental effects of hydroxyl radicals on human sperm functions may be mediated, at least partly, through lipid peroxidation and DNA modification.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1997

Safeguarding the administration of high-dose chemotherapy: a national practice survey by the American Society for Blood and Marrow Transplantation.

Overdoses of high-dose chemotherapy before hematopoietic cell transplantation are serious adverse events, but their frequency and etiology are unknown. The American Society for Blood and Marrow Transplantation (ASBMT) conducted an anonymous national survey to identify errors in safety practices during the administration of high-dose chemotherapy. The questionnaire was returned from 115 (68%) of 170 hematopoietic transplant centers in the United States. Ninety-four of the programs were university or affiliated centers, 19 were community hospitals, and 41 were founded since 1990. A total of 7650 transplants were reported for 1994: 22% of the programs performed 1-20 transplants, 60% performed 21-100 transplants, and 18% performed more than 100 transplants. Fifteen of the 115 responding centers reported a total of 18 patients inadvertently given overdoses of cisplatin (n=3), carboplatin (n=2), busulfan (n=2), cytosine arabinoside (n=2), cyclophosphamide (n=2), interleukin-2 (n=2), or other agents (n=5) between 1989 and 1994. Cumulative drug doses given as a daily dose (six cases) and nursing infusion errors (six cases) were the most common errors. The estimated chemotherapy overdose error rate was 0.06%, or 6 cases/10,000 transplants, with 95% confidence limits of 0.03-0.11%. The overdose rate among more experienced centers in operation before 1990 was lower than that among newer centers (p < 0.01). Large centers (> 100 transplants performed in 1994) experienced errors at rates lower than those in medium-sized centers (21-100 transplants, p = 0.03). Although the number of events was small in this self-reporting survey, overdoses were noted in 13% of the responding centers, especially among more recently established units. Safety practices need to emphasize multidisciplinary checkpoints at the physician, pharmacist, nursing, and institutional levels. Based on these survey results, ASBMT recommendations for further safeguards for high-dose chemotherapy administration are proposed.

Adult↗
PubMed1996

Lipid products of phosphoinositide 3-kinase bind human profilin with high affinity.

To gain insight into the physiological function of phosphoinositide 3-kinase (PI 3-kinase) lipid products, this study examines the interactions of the D-3 phosphoinositides with profilin and the consequent effects on actin dynamics and phosphoinositide turnover. Profilin, a ubiquitous actin-regulating protein, plays a putative role in regulating actin assembly and PLC-gamma 1 signaling in light of its unique interactions with actin and phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2]. Here we raise evidence that the affinity of profilin with the D-3 phosphoinositides is substantially higher than that of PtdIns(4,5)P2. The dissociation constants (Kd) are estimated to be 1.1 microM, 5.7 microM, and 11 microM for phosphatidylinositol 3,4-bisphosphate [PtdIns(3,4)P2], phosphatidylinositol 3,4,5-trisphosphate [PtdIns(3,4,5)P3], and PtdIns(4,5)P2, respectively. Spectroscopic data show that while all these phosphoinositides alter the tryptophan fluorescence of profilin in a similar fashion, the respective conformational effect on profilin is vastly different. Based on CD data, the alpha-helical contents of profilin in the presence of 8 molar equiv of PtdIns(4,5)P2, PtdIns(3,4,5)P3, and PtdIns(3,4)P2 are 17.4%, 11.5%, and 1.4%, respectively, vis-a-vis 9.4% for profilin alone. In contrast, no appreciable change in the fluorescence and CD spectra is observed when related inositol phosphates such as Ins(1,4,5)P3, Ins(1,3,4,5)P4, or Ins(1,3,4)P3 at comparable concentrations are tested. Evidence suggests that this differential recognition bears functional significance concerning the intricate roles of profilin and inositol lipids in modulating actin polymerization and PtdIns(4,5)P2 turnover. The relative potency of individual phosphoinositides in offsetting the inhibitory effect of profilin on actin assembly is PtdIns(3,4)P2 > PtdIns(3,4,5)P3 > PtdIns(4,5)P2, consistent with their relative binding affinity with profilin. Moreover, the inhibitory effect of profilin on PLC-gamma 1-mediated PtdIns(4,5)P2 hydrolysis is overcome by PtdIns(3,4)P2 and PtdIns(3,4,5)P3 through a combined effect of PLC-gamma 1 activation and preferential profilin binding. This D-3 phosphoinositide-mediated regulation may represent a new mechanism for controlling PtdIns(4,5)P2 turnover by PLC-gamma 1.

Actins↗
PubMed1996

Controlling cell attachment on contoured surfaces with self-assembled monolayers of alkanethiolates on gold.

This paper describes a method based on experimentally simple techniques--microcontact printing and micromolding in capillaries--to prepare tissue culture substrates in which both the topology and molecular structure of the interface can be controlled. The method combines optically transparent contoured surfaces with self-assembled monolayers (SAMs) of alkanethiolates on gold to control interfacial characteristics; these tailored interfaces, in turn, control the adsorption of proteins and the attachment of cells. The technique uses replica molding in poly(dimethylsiloxane) molds having micrometer-scale relief patterns on their surfaces to form a contoured film of polyurethane supported on a glass slide. Evaporation of a thin (< 12 nm) film of gold on this surface-contoured polyurethane provides an optically transparent substrate, on which SAMs of terminally functionalized alkanethiolates can be formed. In one procedure, a flat poly(dimethylsiloxane) stamp was used to form a SAM of hexadecanethiolate on the raised plateaus of the contoured surface by contact printing hexadecanethiol [HS(CH2)15CH3]; a SAM terminated in tri(ethylene glycol) groups was subsequently formed on the bare gold remaining in the grooves by immersing the substrate in a solution of a second alkanethiol [HS(CH2)11(OCH2CH2)3OH]. Then this patterned substrate was immersed in a solution of fibronectin, the protein adsorbed only on the methyl-terminated plateau regions of the substrate [the tri(ethylene glycol)-terminated regions resisted the adsorption of protein]; bovine capillary endothelial cells attached only on the regions that adsorbed fibronectin. A complementary procedure confined protein adsorption and cell attachment to the grooves in this substrate.

Animals↗
PubMed1996

Antagonistic effect of inositol pentakisphosphate on inositol triphosphate receptors.

We present evidence that inositol 1,3,4,5,6-pentakisphosphate acts as an antagonist of inositol triphosphate receptors in vitro by dampening the activity of Ca(2+)-mobilizing inositol phosphates. This antagonism bears physiological significance as cells maintain substantial quantities of this phosphoinositol in the cytosol, especially during cell differentiation or proliferation. Over a concentration range from 30 to 150 microM, this pentakisphosphate causes a two- to five-fold increase in the EC50 values of inositol 1,4,5-trisphosphate and other active phosphoinositols in effecting Ca2+ efflux from brain microsomes. This specific inhibition results from competitive receptor binding, and is not noted with inositol hexaphosphate or related metabolites at comparable concentrations. Thus, inositol 1,3,4,5,6-pentakisphosphate in concert with other allosteric modulators may constitute an integral component for the receptor regulation.

Animals↗
PubMed1996

2'-Phospho-cyclic ADP-ribose, a calcium-mobilizing agent derived from NADP.

Cyclic adenosine diphosphoribose (cADPR), a metabolite of NAD, appears to modulate changes in intracellular free Ca2+ levels by activation of ryanodine-sensitive Ca2+ channels. We report here that an ADPR cyclase purified from Aplysia californica readily catalyzes the conversion of NADP to 2'-phospho-cyclic adenosine diphosphoribose (2'-P-cADPR), cyclized at N-1 of the adenine moiety. An enzyme from canine spleen previously shown to contain NAD glycohydrolase, ADPR cyclase, and cADPR hydrolase activities also utilized NADP and 2'-P-cADPR as substrates. The apparent Km value for NADP was 1.6 microM compared with 9.9 microM for NAD, and the Vmax with NADP was twice that with NAD, indicating that 2'-P-cADPR is a likely metabolite in mammalian cells. 2'-P-cADPR was as active as cADPR in eliciting Ca2+ release from rat brain microsomes, but was unable to elicit Ca2+ release following conversion to 2'-P-ADPR by the action of canine spleen NAD glycohydrolase. 2'-P-cADPR and 1-D-myo-inositol 1,4,5-trisphosphate (IP3) appear to act by distinct mechanisms as microsomes desensitized to IP3 still released Ca2+ in response to 2'-P-cADPR and vice versa. Also, inhibition of IP3-induced Ca2+ release by heparin had no effect on release by 2'-P-cADPR. Both 2'-P-cADPR and cADPR appear to act by a similar mechanism based on similar kinetics of Ca2+ release, similar dose-response curves, cross-desensitization, and partial inhibition of release by procaine. The results of this study suggest that 2'-P-cADPR may function as a new component of Ca2+ signaling and a possible link between NADP metabolism and Ca2+ homeostasis.

ADP-ribosyl Cyclase↗
PubMed1996

Stimulation of an insulin receptor activates and down-regulates the Ca2+-independent protein kinase C, Apl II, through a Wortmannin-sensitive signaling pathway in Aplysia.

Activation of tyrosine kinase-linked receptors has been shown to stimulate Ca2+-independent protein kinase C isoforms in nonneuronal cells. We have examined this signaling pathway in the nervous system. Incubating bag cell neurons from the marine mollusk Aplysia californica with concentrations of insulin known to stimulate a tyrosine kinase-linked receptor in these cells persistently activated and down-regulated the Ca2+-independent protein kinase C (Apl II), whereas insulin only transiently activated and did not down-regulate the Ca2+-activated protein kinase C (Apl I). The effects of insulin may be mediated by activation of phosphoinositide 3-kinase because (a) diC16phosphatidylinositol 3,4,5-trisphosphate, a synthetic phosphoinositide 3-kinase product, stimulated autophosphorylation of baculovirus-expressed Apl II, but not of Apl I, and (b) wortmannin, an inhibitor of phosphoinositide 3-kinase, blocked the activation and down-regulation of Apl II by insulin but not the transient activation of Apl I. These results suggest that activators of tyrosine kinase-linked receptors may mediate some of their effects in neurons through activation of Ca2+-independent protein kinase C isoforms.

Androstadienes↗
PubMed1996

Reconsideration of testicular biopsy and follicle-stimulating hormone measurement in the era of intracytoplasmic sperm injection for non-obstructive azoospermia?

To determine the possibility of finding motile spermatozoa and spermatids in patients with high serum follicle stimulating hormone (FSH) and spermatogenetic disorders proven by pathology, 100 cases of male infertility were reviewed. Of these, 71 patients were found to have non-obstructive azoospermia or severe primary spermatogenetic disorders, and 20 had obstructive azoospermia. A prospective study of the most recent 51 cases was conducted. Multiple testicular tissue biopsies were examined by a pathologist and a well-trained gynaecological technician. The findings of spermatozoa, spermatids and serum FSH concentrations were compared among six different histological groups. It was concluded that 51.2% of the non-obstructive azoospermic and failed spermatogenetic patients had spermatids and even motile 'shaking' spermatozoa and should be re-evaluated. In the non-obstructive azoospermic patients here, almost all the motile spermatozoa and spermatids were found in patients with a serum FSH concentration of < 30 mIU/ml. It is suggested that a testicular biopsy should be conducted in every case of non-obstructive azoospermia and spermatogenetic disorder, even in those patients with elevated serum FSH concentrations.

Biopsy↗
PubMed1996

Serum is a potent stimulator of keratinocyte tissue plasminogen activator expression.

The plasminogen activator (PA) proteolytic cascade comprises two enzymes known as urokinase PA (uPA) and tissue PA (tPA), both of which activate plasminogen to plasmin. In normal human epidermis uPA is the predominant PA. In lesional epidermis from patients with a variety of cutaneous diseases, including psoriasis, pemphigus foliaceous, pemphigus, vulgaris, bullous pemphigoid, and benign chronic pemphigus, however, tPA is selectively elevated and becomes the predominant PA activity. The enhanced tPA is likely to be a reaction to the disease challenge rather than an initiating event in these clinically and etiologically diverse lesions. In the present study, cultured human keratinocytes, propagated under serum-free conditions, have been shown to respond to the addition of bovine or human serum with an increase in tPA activity and antigen. Furthermore, tPA is found predominantly in the suprabasal keratinocytes both in lesional epidermis and in stratified cultures that have been incubated for approximately 8 d in the presence of serum. These results suggest a possible mechanism by which epidermal tPA may be increased in diverse cutaneous lesions: The plasma infiltrated into lesional epidermis may stimulate the suprabasal keratinocytes in vivo to express tPA.

Antigens↗
PubMed1996

Pathological and biochemical modifications of renal function in ibuprofen-induced interstitial nephritis.

Use of ibuprofen in patients with asymptomatic renal failure is known to produce acute renal toxicity. One of the manifestations is interstitial nephritis of which the pathogenic mechanism remains unclear. In the present study, this nephrotoxic syndrome was induced in rabbits by giving a single dose of uranyl nitrate, followed by consecutive doses of ibuprofen. This animal model thus allowed the assessment of renal functional and pathological changes associated with ibuprofen use in renal insufficiency. In these rabbits, the major abnormality appeared to be confined to the tubulointerstitial compartment. Microscopic examinations of the renal necropsy specimens showed tubular necrosis and interstitial lymphocytic infiltration. The histological finding of lymphocytic aggregation suggests that this nephrotoxic effect stems from a cytotoxic immune reaction in the interstitium. Moreover, levels of renal 2-arylpropionyl-CoA epimerase, a key enzyme involved in the metabolic inversion of ibuprofen, showed a significant reduction, which may result from the massive destruction of the tubular cells in these animals. These results support the premise that renal insufficiency is a prerequisite factor for ibuprofen-induced interstitial nephritis.

Animals↗
PubMed1996

Evaluation of polymerase chain reaction-restriction enzyme analysis of mycobacteria cultured in BACTEC 12B bottles.

Polymerase chain reaction with restriction enzyme analysis (PRA) was first tested on 15 reference strains and 50 subcultured clinical isolates of mycobacteria according to the reference algorithm by Telenti et al [1]. Next, we evaluated the application of this method to 108 isolates from liquid media (BACTEC 12B). Of them, 15 M. tuberculosis complex and 81 mycobacteria other than tuberculosis (MOTT) had comparable results with both PRA and the BACTEC 460 TB systems. However, seven M. tuberculosis complex and three potentially pathogenic MOTT were identified by PRA rather than the BACTEC TB system. PRA seems to be an efficient method for the identification of mycobacteria to the species level and a good aid to detect potentially pathogenic mycobacteria, especially in mixed mycobacterial cultures.

Humans↗
PubMed1996

Color Doppler sonogrphy in differentiation between testicular torsion and epididymoorchitis: report of three cases.

Clinical assessment of the testicular torsion and epididymoorchitis is inherently difficult. Inadequate clinical information may prevent differentiation testicular torsion from non-surgical condition. We reported 3 cases with symptoms of acute scrotal condition who had received color Doppler sonography. One man had epididymoorchitis and color Doppler sonography showed profusely increased blood flow in the region of epididymis and testis. Symptoms subsided with one week of medical treatment. Sonography correctly detected absence of testicular perfusion in 2 boys who had sugical exploration of the scrotum. Testicular torsions were confirmed by surgical findings. Absence or markedly decreased testicular blood flow which indicated testicular ischemia or infarction was easily identified. Conversely, hyperemia of the testis and/or epididymis is usually associated with inflammation However, incomplete torsion or detorsion may demonstrate normal testicular flow on color Doppler sonography. Color Doppler sonography provides early diagnosis of acute testicular torsion, and prevents unnecessary scrotal exploration.

Adolescent↗
PubMed1996

Detection of cerebral desaturation during cardiopulmonary bypass by cerebral oximetry.

BACKGROUND: As oxygen consumption increases acutely during rewarming period in extracorporeal cardiopulmonary bypass (CPB), it is crucial to maintain cerebral oxygen delivery at this critical moment. The aim of this study was to evaluate the effectiveness of a cerebral oximeter (INVOS 3100, Somanetics Corporation, Troy, MI, USA) in monitoring cerebral oxygen balance during rewarming in CPB by correlating optical spectroscopic determinations with jugular bulb oxyhemoglobin saturation measurements. METHODS: On trial were 15 patients who underwent cardiac surgery under moderate hypothermic nonpulsatile CPB. Infrared spectroscopic soma sensor was placed over the patient's left frontal area to continuously monitor the regional cerebral oxygen saturation (SrO2) and the ipsilateral internal jugular vein was cannulated for measurement of venous oxyhemoglobin saturation (SjO2) at the jugular bulb. The changes of SjO2, SrO2, mean arterial pressure (MAP) and nasopharyngeal temperature (NPT) were recorded 5 min before CPB, instantaneously at initiation of CPB and at the point where every increment of 1 degree C in NPT was reached during CPB rewarming. The data obtained were statistically analyzed for any correlation between two methods using repeated measurements of ANOVA and linear regression. RESULTS: There was no correlation between SjO2 and SrO2, between MAP change and SjO2 or SrO2 at the start of CPB, but a significant reduction of SjO2 during rewarming period was observed which was inversely correlative with NPT changes (r(2) = 0.64, p < 0.05). However, SrO2 did not show a similarity. CONCLUSIONS: Jugular bulb desaturation which correlated inversely with rewarming speed as disclosed in this study indicated that the temperature change during rewarming was crucial for cerebral oxygen balance. Being less sensitive and still more unspecific, the INVOS 3100 cerebral oximeter is incapable and not recommended for monitoring cerebral oxygen saturation in CPB.

Aged↗
PubMed1995

Phosphorylation of the platelet p47 phosphoprotein is mediated by the lipid products of phosphoinositide 3-kinase.

Platelet stimulation by thrombin or the thrombin receptor activating peptide (TRAP) results in the activation of phosphoinositide 3-kinase and the production of the novel polyphosphoinositides phosphatidylinositol 3,4-bisphosphate (PtdIns-3,4-P2) and phosphatidylinositol 3,4,5-trisphosphate (PtdIns-3,4,5-P3). We have shown previously that these lipids activate calcium-independent protein kinase C (PKC) isoforms in vitro (Toker, A., Meyer, M., Reddy, K. K., Falck, J. R., Aneja, R., Aneja, S., Parra, A., Burns, D. J., Ballas, L. M. and Cantley, L. C. (1994) J. Biol. Chem. 269, 32358-32367). Activation of platelet PKC in response to TRAP is detected by the phosphorylation of the major PKC substrate in platelets, the p47 phosphoprotein, also known as pleckstrin. Here we provide evidence for two phases of pleckstrin phosphorylation in response to TRAP. A rapid phase of pleckstrin phosphorylation (< 1 min) precedes the peak of PtdIns-3,4-P2 production and is unaffected by concentrations of wortmannin (10-100 nM) that block production of this lipid. However prolonged phosphorylation of pleckstrin (> 2 min) is inhibited by wortmannin concentrations that block PtdIns-3,4-P2 production. Phorbol ester-mediated pleckstrin phosphorylation was not affected by wortmannin and wortmannin had no effect on purified platelet PKC activity. Phosphorylation of pleckstrin could be induced using permeabilized platelets supplied with exogenous gamma-32P[ATP] and synthetic dipalmitoyl PtdIns-3,4,5-P3 and dipalmitoyl PtdIns-3,4-P2 micelles, but not with dipalmitoyl phosphatidylinositol 3-phosphate or phosphatidylinositol 4,5-bisphosphate. These results suggest two modes of stimulating pleckstrin phosphorylation: a rapid activation of PKC (via diacylglycerol and calcium) followed by a slower activation of calcium-independent PKCs via PtdIns-3,4-P2.

Androstadienes↗