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At least 19 recordsLinked to original sources
PubMed2005

Perpendicular magnetization in self-assembled films of citrate-capped gamma-Fe2O3 nanocrystals on Si(100) surfaces.

gamma-Fe2O3 nanocrystals capped with citrate and octylamine have been chemically prepared. The octylamine-capped nanocrystals exhibit a tendency to form ordered lattices. Films of nanocrystals of varying thickness (454, 720, and 1400 microg/cm2 in the case of citrate-capped nanocrystals and 300 microg/cm2 in the case of octylamine-capped nanocrystals) have been prepared on Si(100) substrates by drop casting and have been characterized by X-ray diffraction, scanning electron microscopy, and atomic force microscopy. Magnetic measurements have been carried out on the films as well as on nanocrystal powders. The films of citrate-capped gamma-Fe2O3 nanocrystals exhibit enhanced perpendicular magnetization, with the anisotropy depending on the film thickness.

Amines↗
PubMed1982

Fungistatic capacity of sera from guinea pigs injected with various iron solutions: differences between Trichophyton mentagrophytes and Rhizopus oryzae.

The fungistatic capacity and serum ion levels (SI) of guinea pigs given subcutaneous injections of various iron solutions were examined. The administration of 2.0 ml of 0.1 M ferric ammonium sulfate, ferric sulfate, or ferric chloride subcutaneously had no significant effect on the SI 3 h after administration, whereas ferric ammonium citrate, ferric citrate, or ferrous sulfate elevated the SI to 50 to 140 times that necessary to saturate the unbound transferrin in normal sera. The sera from 11 of 15 guinea pigs with an elevated SI remained fungistatic for Trichophyton mentagrophytes, whereas 3 of 15 guinea pigs with an elevated SI remained fungistatic for Rhizopus oryzae. The sera from normal guinea pigs were consistently fungistatic for Rhizopus oryzae. The sera from normal guinea pigs were consistently fungistatic for both T. mentagrophytes and R. oryzae. These data suggest that subcutaneous administration of certain iron compounds can significantly elevate the SI without completely abolishing the fungistatic capacity of the serum.

Animals↗
PubMed1982

Characterization of ATP citrate lyase from Chlorobium limicola.

ATP citrate lyase (EC 4.1.3.8) from Chlorobium limicola was partially purified. It was established that the consumption of substrates and the formation of products proceeded stoichiometrically and that citrate cleavage was of the si-type. ADP and oxaloacetate inhibited enzyme activity. Oxaloacetate also inhibited the growth of C. limicola.

ATP Citrate (pro-S)-Lyase↗
PubMed1997

Effects of silicon, citrate and the fasting state on the intestinal absorption of aluminium in rats.

1. The effect of silicon (Si) contained in drinking water and solid food on the intestinal absorption of aluminium (Al) remains a matter of debate. The present study was designed to readdress this issue in the experimental animal, and to examine concomitantly the effects of citrate and the fasting state, respectively. 2. Three groups of young, non-fasted rats (n = 8 per group) were gavaged by solutions containing 3.8 ng of 26Al, 63 ng of 27Al, and either distilled water (< 0.1 mg/l Si) or commercial mineral water with a medium (6 mg/l) or high (14 mg/l) Si concentration. 3. Two other groups of eight non-fasted rats each received the same distilled water or high-Si gavage solution, respectively, together with a high citrate concentration (62 g/l). In each case the animals had free access to drinking water for 5 days before and 2 days after the gavage, containing the same Si concentration as in the gavage solution. A sixth group of eight rats was gavaged by low-Si, Al and distilled water in the fasted state. 4. The animals were killed 48 h after gavage, and blood, tissue and urine samples were collected for 26Al measurements by accelerator mass spectrometry. 5. We found that the fraction of absorbed 26Al retained in the skeleton (0.025-0.030%) was of the same order of magnitude as the fraction excreted in the 48 h urine (0.035-0.037%). High Si concentrations in the drinking water failed to depress the 26Al fraction absorbed, as estimated on the basis of skeletal accumulation and urinary excretion. 6. The administration of citrate-containing fluid enhanced 26Al absorption 5- to 10-fold (P < 0.005), but again the Si content of drinking water did not interfere. Finally, the intestinal absorption of 26Al was approximately 15 times higher in the fasted than in the non-fasted state. 7. In conclusion, the provision of large amounts of Si in the drinking water failed to modify physiological intestinal Al absorption under basal conditions or after its stimulation by citrate. However, a prolonged fast greatly enhanced Al absorption, compared with the non-fasted state.

Aluminum↗
PubMed1996

Dissolution kinetics of a lunar glass simulant at 25 degrees C: the effect of pH and organic acids.

The dissolution kinetics of a simulated lunar glass were examined at pH 3, 5, and 7. Additionally, the pH 7 experiments were conducted in the presence of citric and oxalic acid at concentrations of 2 and 20 mM. The organic acids were buffered at pH 7 to examine the effect of each molecule in their dissociated form. At pH 3, 5, and 7, the dissolution of the synthetic lunar glass was observed to proceed via a two-stage process. The first stage involved the parabolic release of Ca, Mg, Al, and Fe, and the linear release of Si. Dissolution was incongruent, creating a leached layer rich in Si and Ti which was verified by transmission electron microscopy (TEM). During the second stage the release of Ca, Mg, Al, and Fe was linear. A coupled diffusion/surface dissolution model was proposed for dissolution of the simulated lunar glass at pH 3, 5, and 7. During the first stage the initial release of mobile cations (i.e., Ca, Mg, Al, Fe) was limited by diffusion through the surface leached layer of the glass (parabolic release), while Si release was controlled by the hydrolysis of the Si-O-Al bonds at the glass surface (linear release). As dissolution continued, the mobile cations diffused from greater depths within the glass surface. A steady-state was then reached where the diffusion rate across the increased path lengths equalled the Si release rate from the surface. In the presence of the organic acids, the dissolution of the synthetic lunar glass proceeded by a one stage process. The release of Ca, Mg, Al, and Fe followed a parabolic relationship, while the release of Si was linear. The relative reactivity of the organic acids used in the experiments was citrate > oxalate. A thinner leached layer rich in Si/Ti, as compared to the pH experiments, was observed using TEM. Rate data suggest that the chemisorption of the organic anion to the surface silanol groups was responsible for enhanced dissolution in the presence of the organic acids. It is proposed that the increased rate of Si release is responsible for the one stage parabolic release of mobile cations and the relatively thin leached layer compared to experiments at pH 3 and 5.

Agriculture↗
PubMed1993

Effects of 3,6-dimethamidodibenzopyriodonium citrate on slow inward calcium current in isolated guinea pig ventricular cells.

The effects of 3,6-dimethamidodibenzopyriodonium citrate (I-65) on action potentials and slow inward calcium current (I(si)) were examined on isolated guinea pig ventricular myocardial cells. I-65 (30-100 mumol.L-1) depressed the action potential duration at 20% repolarization (APD20) and, under voltage-clamp conditions, reduced the amplitude of I(si) without changing the I-V relations. I-65 also showed use-dependent effects on I(si). These suggest that I-65 may block I(si) by acting on the inactivated state of Ca channels.

Action Potentials↗
PubMed2004

Chronic prostatitis: MR imaging and 1H MR spectroscopic imaging findings--initial observations.

PURPOSE: To determine whether chronic prostatitis affects three-dimensional proton magnetic resonance (MR) spectroscopic imaging in evaluation of disease in the peripheral zone. MATERIALS AND METHODS: Combined MR imaging and three-dimensional MR spectroscopic imaging data were examined retrospectively in 12 patients with radical prostatectomy specimens that contained regions of chronic prostatitis larger than 6 mm in the peripheral zone. The 6-mm restriction was based on MR spectroscopic imaging spatial resolution of 6.25 mm. Transverse T2-weighted MR images were reviewed for changes in signal intensity (SI): normal, suspicious for cancer (nodular focal low SI), or indeterminate (focal low SI that was not nodular or contour deforming or diffuse low SI). At MR spectroscopic imaging, proton spectra were considered suspicious for cancer if the ratio of choline plus creatine to citrate was more than 2 SDs above normal mean peripheral zone values. RESULTS: In the 12 patients, mean pretreatment prostate-specific antigen level was 5.77 +/- 2.07 (SD), and median biopsy Gleason score for the gland was 6. At MR imaging in the area of histopathologically confirmed chronic prostatitis, seven of 12 patients had focal low SI that was not nodular (contour deforming) over a region in and around the pathologically defined focus of chronic prostatitis. MR imaging in one patient showed diffuse low SI that correlated with a diffuse area of chronic prostatitis at pathologic examination. MR imaging in another patient showed nodular focal low SI that was suspicious for cancer and corresponded to a focus of chronic prostatitis at pathologic examination. The remaining three patients had no MR imaging abnormality in the region of chronic prostatitis. In the pathologically identified regions of chronic prostatitis, MR spectroscopic imaging data in nine of 12 patients demonstrated elevated choline peak and reduced or no citrate, findings that mimic those of cancer. In two patients, the spectra were normal, and in the remaining patient, the spectra were nondiagnostic. CONCLUSION: At MR spectroscopic imaging, pathologically confirmed chronic prostatitis may demonstrate metabolic abnormality that leads to false-positive diagnosis of cancer. The most common MR imaging finding in chronic prostatitis was focal low SI that was not specific for cancer. In one patient, the MR imaging diagnosis of cancer could not be excluded.

Aged↗
PubMed1988

The chemistry of aluminum and silicon in relation to Alzheimer's disease.

Aluminosilicates have been identified at the core of senile plaques in Alzheimer's disease, and aluminum has been found within neurons bearing neurofibrillary tangles. Here we show that aluminum species interact with silicic acid, Si(OH)4--a normal component of plasma--to form aluminosilicate species solubilized by citrate. A switch in the binding of aluminum from silicate to phosphate at pH less than 6.6 calls attention to the strong binding of cationic aluminum species to proximate phosphate groups, as in the inositol phosphates, and to the potential effect on the activity of the phosphoinositide-derived intracellular messenger system. The chemistry may throw light on the debated relationship between aluminum and Alzheimer's disease.

Aluminum↗
PubMed1993

A novel ovarian stimulation protocol for use with the assisted reproductive technologies.

OBJECTIVE: To determine whether a new ovarian stimulation protocol termed "minimal stimulation" provides pregnancy rates (PRs) comparable with those in a conventional full stimulation protocol for patients undergoing assisted reproductive technologies (ART). DESIGN: Prospective, nonrandomized study of patients in minimal stimulation or full stimulation, followed by standard IVF and zygote intrafallopian transfer or uterine-ET. SETTING: The ART program of the Mayo Clinic, Rochester, Minnesota. PATIENTS: Women (n = 120) 42 years of age or younger with serum day 3 FSH level < or = 15.0 mIU/mL (conversion factor to SI unit, 1.0), normal thyroid-stimulating hormone and PRL levels, normal endometrial cavity as observed on hysterosalpingogram, and partners with a normal semen analysis. INTERVENTIONS: Oral clomiphene citrate, hMG, oocyte retrieval, IVF-ET. MAIN OUTCOME MEASURES: Cancellations, implantation, pregnancy. RESULTS: The cancellation rate was not significantly higher in minimal stimulation (25.8%) than in full stimulation (14.1%). Minimal stimulation cycles yielded fewer oocytes per aspiration (3.4 +/- 1.6) than full stimulation (10.1 +/- 5.4). There was no difference in the implantation rates per ET (minimal stimulation, 16.4%; full stimulation, 13.3%) or overall clinical PRs per retrieval (minimal stimulation, 31%; full stimulation, 42%). CONCLUSIONS: Minimal stimulation for IVF is less expensive than full stimulation and minimizes monitoring and patient discomfort. In addition, it produces acceptable PRs and represents an attractive alternative to select patients undergoing ART.

Adult↗
PubMed1995

Evaluation of the reproductive performance of women with elevated day 10 progesterone levels during ovarian reserve screening.

OBJECTIVES: To evaluate the relationship of elevated day 10 P levels (> or = 1.1 ng/mL, conversion factor to SI unit, 3.18) during ovarian reserve screening and reproductive performance. DESIGN: Prospective screening with longitudinal follow-up. INTERVENTIONS: One hundred seven women underwent ovarian reserve screening with a clomiphene citrate challenge test. MAIN OUTCOME MEASURES: Serum FSH, LH, and E2 levels were determined on cycle day 3 and FSH, LH, and P levels were determined on day 10. A fertility evaluation was completed and a treatment plan was instituted. RESULTS: Twenty-two of 107 (20.6%) women had day 10 P levels > or = 1.1 ng/mL. Women with elevated day 10 P levels were similar in age to women with normal day 10 P levels (< or = 0.9 ng/mL) but had significantly shorter menstrual cycles, higher day 3 and day 10 FSH levels, higher day 3 E2 levels, and higher day 10 LH levels than women with normal day 10 P levels. During ovarian hyperstimulation, women with elevated day 10 P levels required more ampules of hMG, had lower peak E2 levels, and had fewer mature follicles than women with a normal day 10 P level. Sixteen of 85 (18.8%) women with normal day 10 P levels became pregnant, but none of the 22 women with elevated day 10 P levels became pregnant. The incidence of diminished ovarian reserve was higher in women with elevated day 10 P levels (13/22; 59%) when compared with women with a normal day 10 P levels (9/85; 10.6%). CONCLUSIONS: Elevated day 10 P levels (> or = 1.1 ng/mL) during ovarian reserve screening is associated with diminished ovarian reserve and correlates with menstrual cycle parameters associated with a short follicular phase and poor reproductive performance.

Adult↗
PubMed1996

The importance of endogenous feedback for monofollicular growth in low-dose step-up ovulation induction with follicle-stimulating hormone in polycystic ovary syndrome: a randomized study.

OBJECTIVE: To evaluate the role of endogenous feedback in monofollicular growth during low-dose gonadotrophin therapy in polycystic ovary syndrome (PCOS) by measuring FSH levels in a group of patients cotreated with a GnRH agonist (GnRH-a) (group B) compared with patients not cotreated with an agonist (group A). DESIGN: Prospective randomized study. SETTING: University tertiary care Reproductive Endocrinology Unit. PATIENTS: Women with clomiphene citrate-resistant PCOS. MAIN OUTCOME MEASURES: Follicle-stimulating hormone, E2, and inhibin levels, follicular growth. RESULTS: In group A, FSH levels decreased significantly from 7.3 mIU/mL (conversion factor to SI unit, 1.00) at day -5 to 5.9 mIU/mL at day 0 (day that hCG was administered) despite a constant dose, whereas they remained at a level of 7.4 mIU/mL in group B. The rate of monofollicular growth was significantly higher in group A (80%) than in group B (22%). No significant differences in E2 levels or inhibin levels were found between the groups. CONCLUSIONS: The absence of a decrease of FSH during GnRH-a treatment in association with a lower rate of monofollicular growth suggests that endogenous feedback during low-dose step-up ovulation induction in PCOS plays an important role. The absence of this feedback mechanism in the presence of normal inhibin levels suggests that negative feedback control by inhibin during follicular stimulation is minimal.

Adult↗
PubMed1995

A new system for fallopian tube sperm perfusion leads to pregnancy rates twice as high as standard intrauterine insemination.

OBJECTIVE: To evaluate the relative efficacy of a new system for fallopian tube sperm perfusion in comparison with standard IUI in controlled ovarian hyperstimulation (COH) cycles. DESIGN: Prospective randomized trial. SETTING: Ovulation induction program of a tertiary outpatient care center, Hôpital Antoine Béclère, Clamart, France. PATIENTS: We studied 74 infertile women aged 20 to 38 years undergoing 100 cycles of COH from December 1993 to May 1994 only excluding cases of age > 38 years, obstructed or severely damaged fallopian tubes, E2 levels per mature follicle < 250 pg/mL (conversion factor to SI unit, 3.671) on the day of hCG administration, spontaneous LH surge, and cases of marked sperm abnormalities. INTERVENTIONS: Controlled ovarian hyperstimulation was achieved using three types of ovarian stimulation protocols: clomiphene citrate (CC) and hMG (n = 35). hMG alone (n = 35) or GnRH agonist and FSH and hMG (n = 30). Thirty-six hours after hCG administration, patients were assigned randomly to either IUI (group A, n = 50) or fallopian tube sperm perfusion (group B, n = 50). Intrauterine insemination was performed with 0.2 mL of sperm suspension according to a standard technique. Fallopian tube sperm perfusion was performed using a simple and reliable system that ensures a good cervical seal and allows to a pressurized injection of 4 mL of sperm suspension. MAIN OUTCOME MEASURES: Feasibility of the fallopian tube sperm perfusion method, clinical pregnancy (presence of gestational sac with heart beats at 6 weeks of amenorrhea), and ongoing pregnancy rates (PRs) (> 12 weeks of amenorrhea), incidence of complications (multiple pregnancies and ovarian hyperstimulation syndrome [OHSS]). RESULTS: Overall, the new fallopian tube sperm perfusion system was simple to handle and well tolerated by patients. In group A, we observed 10 clinical pregnancies (20% per cycle) of which 7 were ongoing (14%). In group B, 20 clinical pregnancies (40% per cycle) of which 17 ongoing pregnancies (34%) were obtained. These differences were statistically significant. The prevalence of twin and three or more sac pregnancies was similar in the two groups (3/10 and 0/10, respectively, in group A, and 5/20 and 2/20, respectively, in group B). No case of moderate or severe OHSS was observed in this series. CONCLUSIONS: Our results indicate that the new system for fallopian tube sperm perfusion is not only simple and reliable but also may lead to PRs twice as high as standard IUI in COH cycles.

Adult↗
PubMed1999

Genetic organization of the citCDEF locus and identification of mae and clyR genes from Leuconostoc mesenteroides.

In this paper, we describe two open reading frames coding for a NAD-dependent malic enzyme (mae) and a putative regulatory protein (clyR) found in the upstream region of citCDEFG of Leuconostoc mesenteroides subsp. cremoris 195. The transcriptional analysis of the citrate lyase locus revealed one polycistronic mRNA covering the mae and citCDEF genes. This transcript was detected only on RNA prepared from cells grown in the presence of citrate. Primer extension experiments suggest that clyR and the citrate lyase operon are expressed from a bidirectional A-T-rich promoter region located between mae and clyR.

Amino Acid Sequence↗
PubMed1976

Generation of an esterolytic and kinin-forming kallikrein-alpha2-macroglobulin complex in human serum by treatment with acetone.

Kinin-forming and esterolytic activity in human citrate plasma has been activated by treatment of the plasma with acetone. By far most of the esterolytic activity if not all of it was recovered in an alpha2-macroglobulin (alpha2M) kallikrein complex (SI) which was characterized and purified by chromatography. Little if any esterolytic activity was present which could be ascribed to free plasma kallikrein. The alpha2M-kallikrein complex had kinin-releasing activity though much less than free plasma kallikrein, relative to esterolytic potency. This explains that a considerable fraction of the kinin-forming potential of acetone-activated plasma resides in free plasma kallikrein although it represents only a very small portion of the total kallikrein store. Like free plasma kallikrein the alpha2M complex releases kinin from LMW-kininogen less efficiently than from HMW, in systems of purified components. In whole plasma, the efficiencies change: whereas plasma kallikrein is rapidly inactivated by endogenous inhibitors, the alpha2M complex is protected from further inactivation and capable of releasing kinin continuously if slowly, attacking also LMW-kininogen after HMW-kininogen has been consumed by free kallikrein. While the alpha2M-complex in this respect differs functionally from free plasma kallikrein and explains earlier observations suggesting the presence of two kininogenases, it seems doubtful now that two truly different kininogenases exist in human plasma. The results suggest that acetone predominantly inactivates full inhibitors of kallikrein such as C1INH whereas alpha2M is somewhat more resistant and (pre-)-kallikrein even more. Depending on the time and temperature of acetone treatment one obtains more or less total kallikrein and varying proportions of free to bound enzymes. It is likely that acetone does not turly trigger an activation of prekallikrein but supports spontaneous activation by slowing down the control of the feedback reinforcement of this activation, by damaging inhibitors.

Acetone↗
PubMed2003

Sterol regulatory element-binding protein-2 interacts with hepatocyte nuclear factor-4 to enhance sterol isomerase gene expression in hepatocytes.

In the course of an effort to identify unknown targets genes for sterol regulatory element-binding proteins (SREBPs) by PCR, the gene for ATP citrate-lyase was determined to be one such gene. (Sato, R., Okamoto, A., Inoue, J., Miyamoto, W., Sakai, Y., Emoto, N., Shimano, H., and Maeda, M. (2000) J. Biol. Chem. 275, 12497-12502). We here report that gene expression of sterol Delta8-isomerase (SI), which catalyzes the conversion of the 8-ene isomer into the 7-ene isomer in the last steps of the cholesterol biosynthetic pathway, is regulated by SREBPs, mainly by SREBP-2. Luciferase assays using the promoter of the human SI gene revealed that a 200-base pair segment upstream region from the transcription start site contains functional elements required for the activity of the SREBPs, Sp1 and NF-Y. Interestingly, SI gene expression was well regulated by sterols in Caco-2 and HepG2 cells, in contrast with HEK293 and HeLa cells. Overexpression of hepatocyte nuclear factor (HNF)-4 in HEK293 cells augmented expression of SREBP-responsive genes including the SI gene, whereas inactivation of HNF-4 by small interfering RNAs in HepG2 cells reduced the SI gene promoter activity. The in vitro pull-down and in vivo co-immunoprecipitation experiments showed the direct interaction between SREBP-2 and HNF-4. These data provide a novel pathway by which HNF-4 potentiates the SREBP functions and stimulates expression of SREBP-responsive genes in enterohepatic cells.

Animals↗
PubMed1998

Al and Si: their speciation, distribution, and toxicity.

OBJECTIVES: In dialysis patients both aluminum (AI) and silicon (Si) may accumulate. Whereas the toxic effects of AI within this population are clearly established, little is known on the role of Si in the development/protection of particular dialysis-related diseases. A clear insight in the protein binding and speciation of trace elements is important to better understand the mechanisms underlying their toxicity/essentiality. Research in this field however is complex and often prone to analytical difficulties and inaccuracies. DESIGN AND METHODS: In the first part of this review techniques used for speciation studies of AI and Si in biological fluids are discussed. Notwithstanding recent technical advances (a) extraneous metal contamination, (b) unrecognized aspecific binding of metals to proteins, and (c) unwanted interactions with separation equipment such as chromatography columns and ultrafiltration membranes remain important pitfalls and often lead to erroneous conclusions. The factors that determine the speciation of AI and Si and their ultimate tissue distribution and toxicity are dealt with in the second part. Here, experimental data obtained with various speciation techniques are linked to in vivo data on the tissue distribution, localization/toxicity of both elements. CONCLUSIONS: A model in which the AI tissue distribution/toxicity is mediated by either its citrate or transferrin bound form is proposed.

Aluminum↗
PubMed2003

[Clinical study of sildenafil in the treatment of premature ejaculation complicated by erectile dysfunction].

OBJECTIVES: To evaluate the efficacy and safety of sildenafil citrate in the treatment of premature ejaculation (PE) complicated by erectile dysfunction (ED). METHODS: Forty-five patients of PE complicated by ED received flexible doses of sildenafil from 50 to 100 mg for 1 to 3 months. Intravaginal ejaculatory latency time (IELT) and sexual satisfaction ratio (SSR) of partner were recorded to evaluate the effect of PE treatment, as well as the general efficacy and satisfaction of ED treatment. And the difference of IIEF-5 before and after the treatment were compared. RESULTS: Twenty-seven patients had their PE improved and the effective rate was 60%. Forty patients reported the improvement in erection and the percentage of erectile improvement was 88.88%. All the 27 patients with improvement of PE achieved effective erection through the administration of 50 mg sildenafil and the satisfaction rate reached 81.48%. On the other hand, only 1 case (5.56%) reported satisfaction over the treatment in the 18 patients who did not obtain improvement of PE. Between the PE improvement group and non-improvement group, there were significant differences (P < 0.001) shown in IIEF-5 scores before and after the treatment. Mild or moderate side effects were reported in 9 patients(20%), who recovered without any treatment. CONCLUSIONS: To premature ejaculation patients with ED, sildenafil can safely and effectively improve their erectile function, the satisfaction over the ED treatment outcome means that their PE symptoms could be alleviated.

Adult↗