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At least 667 records · Page 37Linked to original sources
PubMed1992

Secondary ion emission from solutions: time dependence and surface phenomena.

The temporal behavior of FAB mass spectra from glycerol solutions of tetradecyltrimethylammonium bromide (C14H29-N(CH3)3Br, TTAB) and tetraethylammonium iodide (TEAI) was investigated. FAB spectra of the TTAB solution displayed a continuous decrease in TTA+ with time. Spectra obtained from the TEAI solution were initially invariant for several minutes and then displayed a gradual increase in the relative abundance of TEA+ to a maximum, followed by a precipitous drop in ion intensity. Secondary ion images of droplets of TTAB solution showed that emission of both TTA+ and glycerol secondary ions was homogeneous across the sample. Secondary ion images of droplets of TEAI solution showed heterogeneous and segregated emission of both TEA+ and protonated glycerol. Results from the FAB spectra and the secondary ion images were correlated and rationalized on the basis of surface tension-induced mass transport and matrix evaporation.

Ions↗
PubMed1990

A novel minimum ribozyme with oxidoreduction activity.

A nucleoside catalyzing the oxidoreduction of NADH and K3Fe(CN)6 was isolated from Torula yeast RNA and also obtained in 0.05% yield by a series of steps: SDS-phenol extraction, nuclease P1 digestion, alkaline phosphatase digestion, anion exchange chromatography, and HPLC on an ODS column. Its chemical structure was clearly determined at 5-hydroxycytidine, from the results of FAB-MS and 1H and 13C NMR spectroscopies. The mass spectra, chromatographic behavior, UV spectra, and NMR spectra of this nucleoside from natural and synthetic sources were identical. This is the first report of an RNA catalyst having catalytic activity except for the cleavage and ligation of phosphodiester bonds of RNA. That an RNA has oxidoreduction activity indicates new possibilities for RNAs as "living molecules". 5-Hydroxycytidine may be a vestige of RNAs that formerly possessed metabolizing ability.

Cryptococcus↗
PubMed1972

Formation of binaries from triple systems.

The dynamical behavior of three masses moving under their mutual gravitational attraction in a plane is investigated by a systematic series of numerical experiments. It is shown that in 73% of the cases, a triple system disintegrates in less than 150 time units (corresponding to about 150 crossing times), and a binary is formed with the third star that escapes at hyperbolic velocity. The average time for disintegration is of the order of 10(9) years for triple stellar systems, as well as for triple galaxies. The statistics of the escaping masses show that the escaping mass is usually, but not always, the smallest in the system. A simple equation, giving the balance between the negative energy stored in the binary and the positive energy necessary for escape, explains the results qualitatively.

Journal Article↗
PubMed2003

Synthesis of betaine-homocysteine S-methyltransferase is continuously enhanced in fatty livers of thyroidectomized chickens.

We examined thyroidectomized chickens in terms of plasma lipid concentration and protein expression within the liver. Although the body weight of thyroidectomized chickens was remarkably low due to growth retardation, the livers were enlarged and fatty compared to those of sham-operated chickens. An increase in phospholipid, triglyceride, and total cholesterol levels within the blood plasma of thyroidectomized chickens was observed, clearly reflecting increased lipid synthesis within the liver. Overexpression of some proteins, for example, 29- and 45-kDa proteins, was observed in thyroidectomized chicken livers by means of electrophoresis. A peptide map was made for the protein that exhibited the greatest degree of overexpression. One of them demonstrated a molecular mass of 45 kDa and an isoelectric point (pI) between 7.5 and 8.0, depending on its form. Partial N-terminal amino acid sequences were determined from three random peptides of this protein. The amino acid sequence of this protein showed a high degree of homology with the betaine-homocysteine S-methyltransferase (BHMT, EC 2.1.1.5) of some mammalian species. We identified this protein as chicken BHMT because, in addition to its sequence homology with mammalian BHMT, there were similarities were also observed between this 45-kDa protein and mammalian BHMT with respect to molecular mass and isoelectric behavior. In the liver, 10 d after thyroidectomy, the synthesis of hepatic BHMT had already been enhanced, and the high expression was maintained at 50 d of age. Generally, BHMT catalyzes the transfer of a methyl group from betaine to L-homocysteine. In addition, it seems that this enzyme is also closely related to lipid metabolism in the liver; in this study expression of BHMT in the liver corresponded to plasma lipid levels. Moreover, hypothyroidism may be directly or indirectly related to overexpression of BHMT. Due to similarities between the BHMT of chickens and mammalian species, the chicken model might provide a useful means by which to study BHMT, its role in lipid metabolism, and methods of targeting the expression of BHMT. Another 29-kDa protein was unidentified in the homology search.

Adipose Tissue↗
PubMed2004

Thermodynamic and transport measurements of superconducting Na0.3CoO2.1.3H2O single crystals prepared by electrochemical deintercalation.

Superconducting single crystal samples of Na0.3CoO2.1.3H(2)O have been produced using an electrochemical technique which dispenses with the usual bromine chemical deintercalation method. In fully hydrated crystals, susceptibility and specific heat measurements confirm that bulk superconductivity has been achieved. The extracted normal state density of states indicates Fermi-liquid behavior with strong mass enhancement and a modest Wilson ratio. Measurements of H(c2) for H parallel c and H parallel ab reveal significant anisotropy, and the extracted value for the coherence length is about 100 A, consistent with an extremely narrow bandwidth.

Journal Article↗
PubMed2004

Strongly enhanced magnetic fluctuations in a large-mass layered ruthenate.

We have studied the magnetic excitations in Ca2-xSrxRuO4, x=0.52 and 0.62, which exhibit an anomalously high susceptibility and heavy mass Fermi liquid behavior. Our inelastic neutron scattering experiments reveal strongly enhanced magnetic fluctuations around an incommensurate wave-vector (0.22,0,0) pointing to a magnetic instability. The magnetic fluctuations show no correlation in the c direction and also along the RuO2 planes the signal is extremely broad, Deltaq=0.45 A(-1). These fluctuations can quantitatively account for the high specific heat coefficient and relate to the high macroscopic susceptibility. The magnetic scattering is attributed to the d(xy) band, the active band for spin triplet superconductivity in Sr2RuO4.

Journal Article↗
PubMed1990

Microtubule-associated-protein (MAP) kinase activated by nerve growth factor and epidermal growth factor in PC12 cells. Identity with the mitogen-activated MAP kinase of fibroblastic cells.

Treatment of PC12 cells with either nerve growth factor (NGF), a differentiating factor, or epidermal growth factor (EGF), a mitogen, resulted in 7-15-fold activation of a protein kinase activity in cell extracts that phosphorylated microtubule-associated protein (MAP) 2 on serine and threonine residues in vitro. Both the NGF-activated kinase and the EGF-activated kinase could be partially purified by sequential chromatography on DEAE-cellulose, phenyl-Sepharose and hydroxylapatite, and were identical with each other in their chromatographic behavior, apparent molecular mass (approximately 40 kDa) on gel filtration, substrate specificity, and phosphopeptide-mapping pattern of MAP2 phosphorylated by each kinase. Moreover, both kinases were found to be indistinguishable from a mitogen-activated MAP kinase previously described in growth-factor-stimulated or phorbol-ester-stimulated fibroblastic cells, based on the same criteria. Kinase assays in gels after SDS/polyacrylamide gel electrophoresis revealed further that the NGF- or EGF-activated MAP kinase in PC12 cells, as well as the EGF-activated MAP kinase in fibroblastic 3Y1 cells resided in two closely spaced polypeptides with an apparent molecular mass of approximately 40 kDa. In addition, these MAP kinases were inactivated by either acid phosphatase treatment or protein phosphatase 2A treatment. These results indicate that MAP kinase may be activated through phosphorylation by a differentiating factor as well as by a mitogen. MAP kinase activation by EGF was protein kinase C independent; it reached an almost maximal level 1 min after EGF treatment and subsided rapidly within 30-60 min. On the other hand, NGF-induced activation of MAP kinase was partly protein kinase C dependent and continued for at least 2-3 h.

Adrenal Gland Neoplasms↗
PubMed2005

Clomiphene citrate effects on testosterone/estrogen ratio in male hypogonadism.

AIM: Symptomatic late-onset hypogonadism is associated not only with a decline in serum testosterone, but also with a rise in serum estradiol. These endocrine changes negatively affect libido, sexual function, mood, behavior, lean body mass, and bone density. Currently, the most common treatment is exogenous testosterone therapy. This treatment can be associated with skin irritation, gynecomastia, nipple tenderness, testicular atrophy, and decline in sperm counts. In this study we investigated the efficacy of clomiphene citrate in the treatment of hypogonadism with the objectives of raising endogenous serum testosterone (T) and improving the testosterone/estrogen (T/E) ratio. METHODS: Our cohort consisted of 36 Caucasian men with hypogonadism defined as serum testosterone level less than 300 ng/dL. Each patient was treated with a daily dose of 25 mg clomiphene citrate and followed prospectively. Analysis of baseline and follow-up serum levels of testosterone and estradiol levels were performed. RESULTS: The mean age was 39 years, and the mean pretreatment testosterone and estrogen levels were 247.6 +/- 39.8 ng/dL and 32.3 +/- 10.9, respectively. By the first follow-up visit (4-6 weeks), the mean testosterone level rose to 610.0 +/- 178.6 ng/dL (P < 0.00001). Moreover, the T/E ratio improved from 8.7 to 14.2 (P < 0.001). There were no side effects reported by the patients. CONCLUSIONS: Low dose clomiphene citrate is effective in elevating serum testosterone levels and improving the testosterone/estradiol ratio in men with hypogonadism. This therapy represents an alternative to testosterone therapy by stimulating the endogenous androgen production pathway.

Adult↗
PubMed1968

Cytokinin from soluble RNA of Escherichia coli: 6-(3-methyl-2-butenylamino)-2-methylthio-9-beta-D-ribofuranosylpurine.

We have isolated a compound responsible for the cytokinin activity of soluble RNA from Escherichia coli. The structure, indicated as 6-(3-methyl-2-butenylamino)-2-methylthio-9-beta-D-ribofuranosylpurine, C(16)H(23)N(5)0(4)S, on the basis of low-and high-reso!ution mass spectrometry, was established by unequivocal synthesis. The mass spectra, chromatographic behavior, and ultraviolet spectra of the compounds from natural and synthetic sources were identical.

Chromatography, Paper↗
PubMed1999

Effect of vitamin D(3) treatment in the neonatal or adolescent age (hormonal imprinting) on the thymic glucocorticoid receptor of the adult male rat.

Single neonatal treatment with 25 microg vitamin D(3) significantly decreased the thymic glucocorticoid receptor density (B(max)) of 6-week-old male rats. In females, a similar treatment did not cause any changes. Single vitamin D(3) treatment (50 microg) during adolescence (i.e. 6-week-old animals) significantly increased the glucocorticoid receptor density in adult (10-week-old) males. No significant changes in receptor affinity (K(d)) could be observed. Considering that in earlier experiments similar neonatal treatments influenced bone mineral mass and sexual behavior, the hormonal imprinting effect of vitamin D(3) and its harmful effect on the development of other members of the steroid receptor superfamily, seems to be unquestionable.

Aging↗
PubMed1992

Association between rheology and components of lipoproteins in human blood. Results from the MONICA project.

BACKGROUND: Recent studies have suggested that several hemostatic factors, leukocyte count, and plasma viscosity are predictive of coronary heart disease. Detailed analyses on lifestyle correlates, in particular plasma lipids and lipoproteins, of determinants of blood rheology have not been reported from epidemiological studies. METHODS AND RESULTS: We studied the relation between determinants of blood rheology and components of lipoproteins in a large sample of a population aged 25-64 years. The rheological parameters investigated were plasma viscosity, hemoglobin, and total serum protein; the lipoprotein variables included total cholesterol, high density lipoprotein (HDL) cholesterol, and the apoproteins A-I, A-II, and B. Covariables considered for possible confounding effects were age, body mass index, smoking behavior, alcohol consumption, and hypertension. Plasma viscosity was found to have a positive linear association with total cholesterol and apoprotein B (partial correlations after adjustment for all covariables including total serum protein for men and women were r = 0.23/0.19 and 0.24/0.25, respectively) and a small negative linear association with HDL cholesterol (r = -0.14/-0.10) and with apoprotein A-I (r = -0.08/-0.06). Polynomial regression showed a strong quadratic relation with HDL cholesterol in men, whereas no other variable revealed an appreciable deviation from linearity. The covariables had only a small, if any, confounding effect. Total serum protein, after control for the covariables, appeared to be associated only with total cholesterol. No association was found with hemoglobin. CONCLUSIONS: We conclude that rheological mechanisms may be involved in the pathogenesis of ischemic syndromes in hyperlipidemias. However, the finding that in particular men with very low HDL cholesterol exhibit increased plasma viscosity cannot be explained in pure rheological terms but may be, at least in part, the result of concomitant hypertriglyceridemia. This was not assessed in this study.

Adult↗
PubMed1989

Photoperiodic control of reproduction and molt in the kestrel, Falco tinnunculus.

An adaptive decline in average clutch size with progressive date of laying is characteristic of most bird species with a single clutch of variable size per year. The effect of photoperiod on timing of laying, clutch size, and subsequent molt was investigated in kestrel pairs breeding and raising their young in captivity. In natural daylight (nLD), clutch size, under ad libitum feeding, showed the same decline with date as in nature. Birds breeding later also started molt later and molted faster (more feathers simultaneously), so that all birds completed molt more or less at the same time. Constant long days (LD 17.5:6.5 and LD 13:11) from December 1 onward advanced both reproduction and molt. The LD 17.5:6.5 group developed the reproductive system faster, had a shorter courtship period, and laid eggs earlier than the LD 13:11 group. In both photoperiods there was a decrease in clutch size with progressive laying date, similar to that in nLD. Molt started in both groups at about the end of the laying period and slowed down in the longer photoperiod, especially in males. Plasma luteinizing hormone (LH) changes in the two photoperiods were different for males and females. Males showed the expected slower LH response in the shorter photoperiod, but the initial LH response by females was the same in both photoperiods. Data on LH, reproductive behavior, and body mass suggest that females have a wider annual reproductive window than males. Data on time of laying and number of eggs suggest that clutch size in the kestrel is determined by laying date itself, following an endogenous rhythm that is phase-locked to the reproductive cycle.

Androgens↗
PubMed1998

Development of eating behaviors among children and adolescents.

The prevalence of obesity among children is high and is increasing. We know that obesity runs in families, with children of obese parents at greater risk of developing obesity than children of thin parents. Research on genetic factors in obesity has provided us with estimates of the proportion of the variance in a population accounted for by genetic factors. However, this research does not provide information regarding individual development. To design effective preventive interventions, research is needed to delineate how genetics and environmental factors interact in the etiology of childhood obesity. Addressing this question is especially challenging because parents provide both genes and environment for children. An enormous amount of learning about food and eating occurs during the transition from the exclusive milk diet of infancy to the omnivore's diet consumed by early childhood. This early learning is constrained by children's genetic predispositions, which include the unlearned preference for sweet tastes, salty tastes, and the rejection of sour and bitter tastes. Children also are predisposed to reject new foods and to learn associations between foods' flavors and the postingestive consequences of eating. Evidence suggests that children can respond to the energy density of the diet and that although intake at individual meals is erratic, 24-hour energy intake is relatively well regulated. There are individual differences in the regulation of energy intake as early as the preschool period. These individual differences in self-regulation are associated with differences in child-feeding practices and with children's adiposity. This suggests that child-feeding practices have the potential to affect children's energy balance via altering patterns of intake. Initial evidence indicates that imposition of stringent parental controls can potentiate preferences for high-fat, energy-dense foods, limit children's acceptance of a variety of foods, and disrupt children's regulation of energy intake by altering children's responsiveness to internal cues of hunger and satiety. This can occur when well-intended but concerned parents assume that children need help in determining what, when, and how much to eat and when parents impose child-feeding practices that provide children with few opportunities for self-control. Implications of these findings for preventive interventions are discussed.

Adipose Tissue↗
PubMed2004

Lifestyle risk factors for chronic disease by family origin among children in multiethnic, low-income, urban neighborhoods.

OBJECTIVES: To describe the prevalence of lifestyle risk factors (LRF) for chronic disease by family origin (FO) among children in multiethnic, low-income, urban neighborhoods. DESIGN: Cross-sectional analysis. SETTING: 16 elementary schools located in disadvantaged, multiethnic neighborhoods in Montreal, Canada. PARTICIPANTS: 4659 schoolchildren aged 9-12 in grades 4-6. OUTCOME MEASURES: Smoking, level of physical activity, dietary habits, body mass index, sedentary behavior. METHODS: Subjects completed self-report questionnaires on sociodemographic characteristics and lifestyle behaviors; height and weight were measured in a standardized protocol. Fourteen FO groupings were identified based on language(s) spoken and countries of birth of both subjects and parents. We tested FO as an independent correlate of having 2 or more LRF, using the generalized estimating equations method. RESULTS: Relative to Canadian children, a higher proportion of Haitian, Portuguese, and other Central American/Caribbean children had 2 or more LRF, the proportion was similar among Cambodian, Vietnamese, Chinese, South American, East European, Arabic, Italian, and South Asian children, and lower among Salvadorean children. CONCLUSION: Prevention programs for youth should take differential distribution of LRF by ethnicity into account.

Attitude to Health↗
PubMed2005

[Nonpharmacological prevention and treatment for osteoporosis].

Treatment of osteoporosis includes prevention for further bone loss, treatment of fracture-related pain, building bone mass, and modifying behavior to prevent fracture and/or falls. Improvement of nutritional intake to prevent bone loss, increasing physical activity or exercise training to prevent bone loss or occurrence of falls and/or fracture, and modifying environmental risk factors are essential as nonpharmacological treatment for osteoporosis. The combination of pharmacologic and nonpharmacologic intervention is fundamental to the management of osteoporosis.

Aged↗
PubMed1992

Redox ribonucleosides. Isolation and characterization of 5-hydroxyuridine, 8-hydroxyguanosine, and 8-hydroxyadenosine from Torula yeast RNA.

Three hydroxyribonucleosides catalyzing the oxido-reduction of NADH and K3F3(CN)6 were purified from Torula yeast RNA by a series of steps including sodium dodecyl sulfate/phenol extraction, nuclease P1 digestion, alkaline phosphatase digestion, anion-exchange chromatography, and high performance liquid chromatography on an ODS column. Analysis by fast atom bombardment-mass spectrometry and 1H and 13C NMR spectroscopy led to identification of the redox ribonucleosides as 5-hydroxyuridine, 8-hydroxyguanosine, and 8-hydroxyadenosine. Their mass spectra, chromatographic behavior, UV spectra, NMR spectra, and IR spectra were identical to those from natural and synthetic sources. Oxidoreduction activities were specific for K3Fe(CN)6 as the oxidant and NADH as the reductant; and their magnitudes decreased in the order 5-hydroxycytidine, 5-hydroxyuridine, 8-hydroxyguanosine, and 8-hydroxyadenosine. The fact that these nucleosides have redox activities suggests new functional roles for RNAs as catalysts.

Adenosine↗
PubMed2006

Ibuprofen fails to prevent brain pathology in a model of neuropsychiatric lupus.

OBJECTIVE: Neurologic and psychiatric manifestations are severe complications of systemic lupus erythematosus (SLE). As commonly seen in patients, spontaneous development of lupus-like disease in MRL-lpr mice is accompanied by brain atrophy and behavioral dysfunction. We examined inflammatory and ultrastructural aspects of central nervous system (CNS) involvement using a nonselective cyclooxygenase-2 (COX-2) inhibitor and measuring effects on behavior, microglial activation, and neuronal morphology. METHODS: Ibuprofen (IBU) was provided in a rodent chow (375 ppm) for animals 5-19 weeks of age. Exploration of a novel environment and performance in the forced swim test assessed effects on behavior. Immunohistochemistry, fluoro-Jade B (FJB) staining, and flow cytometry were employed in neuropathological analysis. Transmission electron microscopy was used to examine ultrastructural morphology of cortical, hippocampal, hypothalamic, nigral, and cerebellar cells. RESULTS: Chronic IBU treatment failed to normalize immune status, behavior, and brain mass in lupus-prone MRL-lpr mice. It also did not reduce density of CD3+ lymphocytes in the choroid plexus, or FJB+ neurons in the hypothalamus. Activated F4/80+ microglia increased with age, but IBU treatment was not effective in reducing their numbers. Although numerous dark cells were seen in functionally critical brain regions (e.g., paraventricular nucleus and subgranular zone), ultrastructural morphologies of classical apoptosis or necrosis were not detected. CONCLUSION: The COX-dependent pathway does not seem to be critical in the etiology of CNS disease in this model of neuropsychiatric lupus. Reduced brain mass, increased microglial activation, and condensation of cytoplasm point to a metabolic perturbation (e.g., excitotoxic damage) that compromises function and survival of central neurons during lupus-like disease.

Animals↗