Biomedical subjects

A Wolf

Publications and source records attributed to A Wolf.

At least 55 records · Page 3Linked to original sources

PubMed2001

Rate measurement of D(0)-->K+pi(-)pi(0) and constraints on D(0) -- D(0) mixing.

We present an observation and time-integrated rate measurement of the decay D(0)-->K(+)pi(-)pi(0) produced in 9 fb(-1) of e(+)e(-) collisions near the Upsilon(4S) resonance. The signal is inconsistent with an upward fluctuation of the background by 4.9 standard deviations. We measured the time-integrated rate of D(0)-->K(+)pi(-)pi(0) normalized to the rate of D(0)-->K(+)pi(-)pi(0) to be 0.0043(+0.0011)(-0.0010) (stat)+/-0.0007 (syst). This decay can be produced by doubly Cabibbo-suppressed decays or by the D(0) evolving into a D(0) through mixing, followed by a Cabibbo-favored decay to K(+)pi(-)pi(0). We also found the CP asymmetry A = (9(+25)(-22))% be consistent with zero.

Journal Article↗

PubMed2001

Experimental investigation of the two-photon widths of the chi(c0) and the chi(c2) mesons.

Using 12.7 fb(-1) of data collected with the CLEO detector at CESR, we observed two-photon production of the cc states chi(c0) and chi(c2) in their decay to pi(+)pi(-)pi(+)pi(-). We measured gamma(gammagamma)(chi(c))xB(chi(c)-->pi(+)pi(-)pi(+)pi(-)) to be 75+/-13(stat)+/-8(syst) eV for the chi(c0) and 6.4+/-1.8(stat)+/-0.8(syst) eV for the chi(c2), implying gamma(gammagamma)(chi(c0)) = 3.76+/-0.65(stat)+/-0.41(syst)+/-1.69(br) keV and gamma(gammagamma)(chi(c2)) = 0.53+/-0.15(stat)+/-0.06(syst)+/-0.22(br) keV. Also, cancellation of dominant experimental and theoretical uncertainties permits a precise comparison of gamma(gammagamma)(chi(c0))/gamma(gammagamma)(chi(c2)), evaluated to be 7.4+/-2.4(stat)+/-0.5(syst)+/-0.9(br), with QCD-based predictions.

Journal Article↗

PubMed2001

Effects of the novel cyclosporine derivative PSC833 on glucose metabolism in rat primary cultures of neuronal and glial cells.

Cyclosporine A (CsA) and the cyclosporine degrees congener PSC833 are known to cause transient CNS symptoms at high dosages in animal and man. Since impaired glucose metabolism plays a fundamental role in many heriditary and drug-induced neurological disorders, it was the purpose of the present study to evaluate whether this mechanism of pathogenesis might apply to PSC833 and CsA, using neural cells from rats. PSC833 and CsA were investigated in primary cultures of rat neuronal and glial cells at the concentration of 0.1, 1, 10, and 20 microM for 24 and 48 hr. Lactate dehydrogenase was determined as a marker of cytotoxicity. Cell proliferation was determined in astrocytes. Cellular glucose metabolism was investigated by 13C-NMR using [1-13C]glucose as a substrate. Glucose and lactate concentrations in the cell culture supernatants were determined spectrophotometrically. PSC833 at 10 microM was not cytotoxic in neuronal or glial cells nor did it inhibit proliferation in astrocytes 24 hr after incubation. Under the same conditions, the determination of [1-13C]glucose and [3-13C]lactate revealed significantly increased glucose consumption and lactate production in both cell types, as well as decreased levels of Krebs cycle intermediates. In the cell culture medium of both cell types after treatment with 10 microM PSC833, the rates of glucose consumption and lactate formation increased in comparison to controls, between 60-83% and 54-78%, respectively. PSC833 (10 microM) and CsA (20 microM) resulted in nearly similar increased glucose consumption and lactate production. The major PSC833 metabolite in rats, M9, which was devoid of CNS effects, did not cause significant changes in glucose metabolism. The present data suggest that PSC833-impaired tricarboxylic acid cycle activity, resulting in decreased Krebs cycle metabolites, can cause energy depletion and acidosis, which might contribute to the transient neurological symptoms of PSC833 and CsA.

Animals↗

PubMed2001

Bounds on the CP asymmetry in b --> sgamma decays.

We have measured the CP asymmetry A(CP) identical with[gamma(b-->sgamma)-gammab-->sgamma)]/[gamma(b-->sgamma)+gamma(b-->sgamma)] to be A(CP) = (-0.079+/-0.108+/-0.022) (1.0+/-0.030), implying that, at 90% confidence level, A(CP) lies between -0.27 and +0.10. These limits rule out some extreme non-standard-model predictions, but are consistent with most, as well as with the standard model.

Journal Article↗

PubMed2001

Study of tau decays to six pions and a neutrino.

The tau decays to six-pion final states have been studied with the CLEO detector at the Cornell Electron Storage Ring. The measured branching fractions are B(tau(-)-->2pi(-)pi(+)3pi(0)nu(tau)) = (2.2+/-0.3+/-0.4)x10(-4) and B(tau(-)-->3pi(-)2pi(+)pi(0)nu(tau)) = (1.7+/-0.2+/-0.2)x10(-4). A search for substructure in these decays shows that they are saturated by intermediate states with eta or omega mesons. We present the first observation of the decay tau(-)-->2pi(-)pi(+)omega(nu)tau and the branching fraction is measured to be (1.2+/-0.2+/-0.1)x10(-4). The measured branching fractions are in good agreement with the isospin expectations but somewhat below the conserved-vector-current predictions.

Journal Article↗

PubMed2001

Observation of new states decaying into Lambda+(c)pi(-)pi(+).

Using 13.7 fb(-1) of data recorded by the CLEO detector at the Cornell Electron Storage Ring, we investigate the spectrum of charmed baryons which decay into Lambda+(c)pi(-)pi(+) and are more massive than the Lambda+(c)(2625) baryon. We find evidence for two new states: one is broad and has an invariant mass roughly 480 MeV above that of the Lambda+(c) baryon; the other is narrow with an invariant mass of 596+/-1+/-2 MeV above the Lambda+(c) mass.

Journal Article↗

PubMed2001

Rate coefficients and final states for the dissociative recombination of LiH+.

The dissociative recombination of LiH+ ions with low-energy electrons is observed at a storage ring and the final states are analyzed using fragment imaging and field ionization techniques. The rate coefficient is found to be larger than its estimated value used in astrophysical models. Mostly the highest energetically possible Rydberg states of the lithium atom are populated by the reaction, indicating a common trend for molecular recombination via the noncrossing mode.

Journal Article↗

PubMed2001

Observation of the Omega(0)(c) Charmed Baryon at CLEO.

The CLEO experiment at the CESR collider has used 13.7 fb(-1) of data to search for the production of the Omega(0)(c) (css ground state) in e(+)e(-) collisions at square root of (s) approximately 10.6 GeV. The modes used to study the Omega(0)(c) are Omega(-)pi(+), Omega(-)pi(+)pi(0), Xi-K-pi(+)pi(+), Xi0K-pi(+), and Omega(-)pi(+)pi(+)pi(-). We observe a signal of 40.4+/-9.0(stat) events at a mass of 2694.6+/-2.6(stat)+/-1.9(syst) MeV/c(2), for all modes combined.

Journal Article↗

PubMed2001

First observation of the decays B(0) --> D(-)p_p pi+ and B(0) --> D(-)p_n.

We report the first observation of exclusive decays of the type B-->D(*)N_NX, where N is a nucleon. Using a sample of 9.7x10(6)B_B pairs collected with the CLEO detector operating at the Cornell Electron Storage Ring, we measure the branching fractions B(B0-->D(*-)p_p pi(+)) = (6.5(+1.3)(-1.2)+/-1.0)x10(-4) and B(B0-->D(*-)p_n) = (14.5(+3.4)(-3.0)+/-2.7)x10(-4). Antineutrons are identified by their annihilation in the CsI electromagnetic calorimeter.

Journal Article↗

PubMed2001

Complete genome sequence of Caulobacter crescentus.

The complete genome sequence of Caulobacter crescentus was determined to be 4,016,942 base pairs in a single circular chromosome encoding 3,767 genes. This organism, which grows in a dilute aquatic environment, coordinates the cell division cycle and multiple cell differentiation events. With the annotated genome sequence, a full description of the genetic network that controls bacterial differentiation, cell growth, and cell cycle progression is within reach. Two-component signal transduction proteins are known to play a significant role in cell cycle progression. Genome analysis revealed that the C. crescentus genome encodes a significantly higher number of these signaling proteins (105) than any bacterial genome sequenced thus far. Another regulatory mechanism involved in cell cycle progression is DNA methylation. The occurrence of the recognition sequence for an essential DNA methylating enzyme that is required for cell cycle regulation is severely limited and shows a bias to intergenic regions. The genome contains multiple clusters of genes encoding proteins essential for survival in a nutrient poor habitat. Included are those involved in chemotaxis, outer membrane channel function, degradation of aromatic ring compounds, and the breakdown of plant-derived carbon sources, in addition to many extracytoplasmic function sigma factors, providing the organism with the ability to respond to a wide range of environmental fluctuations. C. crescentus is, to our knowledge, the first free-living alpha-class proteobacterium to be sequenced and will serve as a foundation for exploring the biology of this group of bacteria, which includes the obligate endosymbiont and human pathogen Rickettsia prowazekii, the plant pathogen Agrobacterium tumefaciens, and the bovine and human pathogen Brucella abortus.

Adaptation, Biological↗

PubMed2001

Impaired fatty acid oxidation in propofol infusion syndrome.

Propofol infusion syndrome is a rare but frequently fatal complication in critically ill children given long-term propofol infusions. We describe a child who developed all the clinical features of propofol infusion syndrome and was treated successfully with haemofiltration. Biochemical analysis before haemofiltration showed a large rise in plasma concentrations of malonylcarnitine (3.3 micromol/L) and C5-acylcarnitine (8.4 micromol/L), which returned to normal after recovery. Abnormalities are consistent with specific disruption of fatty-acid oxidation caused by impaired entry of long-chain acylcarnitine esters into the mitochondria and failure of the mitochondrial respiratory chain at complex 11.

Acidosis↗

PubMed2001

First observation of the sigma(+)(c) baryon and a new measurement of the sigma(+)(c) mass.

Using data recorded with the CLEO II and CLEO II.V detector configurations at the Cornell Electron Storage Rings, we report the first observation and mass measurement of the Sigma(*+)(c) charmed baryon, and an updated measurement of the mass of the Sigma(+)(c) baryon. We find M(Sigma(*+)(c))-M(Lambda(+)(c)) = (231.0+/-1.1+/-2.0) MeV, and M(Sigma(+)(c))-M(Lambda(+)(c)) = (166.4+/-0.2+/-0.3) MeV, where the errors are statistical and systematic, respectively.

Journal Article↗

PubMed2001

Two- and three-body kinematical correlation in the dissociative recombination of H(3)(+).

Fragmentation patterns for dissociative recombination of the triatomic hydrogen molecular ion H(3)(+) in the vibrational ground state have been measured using the storage ring technique and molecular fragment imaging. A broad distribution of vibrational states in the H(2) fragment after two-body dissociation and a large predominance of nearly linear momentum geometries after three-body dissociation are found. The fragmentation results are directly contrasted with Coulomb explosion imaging data on the initial H(3)(+) geometry, compared to existing wave-packet calculations, and considered in the light of a simple physical picture.

Journal Article↗

PubMed2001

Study of B Decays to Charmonium States: B-->eta(c)K and B --> chi(c0)K.

In a sample of 9.66x10(6)B&Bmacr; pairs collected with the CLEO detector we make the first observation of B decays to an eta(c) and a kaon. We measure branching fractions B(B+-->eta(c)K+) = (0.69(+0.26)(-0.21)+/-0.08+/-0.20)x10(-3) and B(B degrees -->eta(c)K degrees ) = (1.09(+0.55)(-0.42)+/-0.12+/-0.31)x10(-3), where the first error is statistical, the second is systematic, and the third is from the eta(c) branching fraction uncertainty. From these we extract the eta(c) decay constant in the factorization approximation, f(eta(c)) = 335+/-75 MeV. We also search for B decays to a chi(c0) and a kaon. No evidence for a signal is found and we set 90% C.L. upper limits: B(B+-->chi(c0)K+)<4.8x10(-4) and B(B degrees -->chi(c0)K degrees )<5.0x10(-4).

Journal Article↗

PubMed2001

A polymorphism, L162V, in the peroxisome proliferator-activated receptor alpha (PPARalpha) gene is associated with lower body mass index in patients with non-insulin-dependent diabetes mellitus.

This study examined the effect a polymorphism (L162V) in the gene for peroxisome proliferator activated receptor (PPAR) alpha in the development of non-insulin-dependent diabetes mellitus (type 2 DM), obesity and hyperlipidaemia. The frequency of the L162V polymorphism in the PPARalpha gene was determined in 370 morbidly obese patients who underwent gastric banding surgery, 154 patients attending a type 2 DM clinic, 188 patients attending a lipid clinic and 199 healthy blood donors. The overall frequency of the V allele of the L162V polymorphism was 0.06. There were no significant differences in the allele frequency between patients with morbid obesity, hyperlipidaemia, type 2 DM and healthy controls, suggesting that it does not play a major role in the development of these conditions. The polymorphism was associated with a lower body mass index (BMI) in two independently recruited groups of patients with type 2 DM. There was no effect of the polymorphism on subjects without type 2 DM. Thus a polymorphism in PPARalpha protects type 2 DM patients from the overweight which is frequently associated with their condition.

Adult↗

PubMed2001

Over-expression of the SUV39H1 histone methyltransferase induces altered proliferation and differentiation in transgenic mice.

The development of multi-cellular organisms is regulated by the ordered definition of gene expression programmes that govern cell proliferation and differentiation. Although differential gene activity is mainly controlled by transcription factors, it is also dependent upon the underlying chromatin structure, which can stabilize transcriptional "on" or "off" states. We have recently isolated human (SUV39H1) and mouse (Suv39h1) histone methyltransferases (HMTases) and shown that they are important regulators for the organization of repressive chromatin domains. To investigate whether a SUV39H1-induced modulation of heterochromatin would affect mammalian development, we generated transgenic mice that over-express the SUV39H1 HMTase early during embryogenesis. SUV39H1 transgenic mice are growth retarded, display a weak penetrance of skeletal transformations and are largely characterized by impaired erythroid differentiation, consistent with highest transgene expression in foetal liver. Ex vivo transgenic foetal liver cultures initially contain reduced numbers of cells in G1 but progress to immortalized erythroblasts that are compromised in executing an erythroid differentiation programme. The outgrowing SUV39H1-immortalized erythroblasts can maintain a diploid karyotype despite deregulation of several tumour suppressor proteins and dispersed distribution of the heterochromatin component HP1. Together, these data provide evidence for a role of the SUV39H1 HMTase during the mammalian development and indicate a possible function for higher-order chromatin in contributing to the balance between proliferation and differentiation potentials of progenitor cells.

Animals↗

PubMed2001

[Doppler ultrasound diagnosis of increased intracranial pressure by comparison of 2 blood flow velocities in the extra- and intracranial segment of the internal carotid artery. 2: Findings in children with increased intracranial pressure].

AIM: We investigated the correlation between intracranial pressure and flow parameters by simultaneous Doppler sonographic flow measurements in the internal carotid arteries and estimation of the intracranial pressure over the anterior fontanelle. METHOD: 12 infants (7 boys and 5 girls) with increased intracranial pressure were investigated. The corrected gestational age at investigation was 42 +/- 14 weeks, the weight was 3080 +/- 2540 g. Intracranial pressure was measured by applanation tonometry over the anterior fontanelle. The infants were subdivided into two groups: Group 1 (9 infants) with slightly increased intracranial pressure (16.9 +/- 3.3 cm H2O) and group 2 (3 infants) with moderately increased intracranial pressure (21.6 +/- 3.3 cm H2O). In all infants Doppler sonographic flow measurements within the intra- and extracranial segments of the internal carotid arteries were performed. From the flow profile, the peak systolic flow velocity Vs, the enddiastolic flow velocity Ved as well as the time average flow velocity TAV and the resistance index RI were measured. From the flow velocities, the I/E-ratio was calculated. The measured variables were compared with the values of matched pairs of a healthy control group of similar age and weight. RESULTS: Group 1 with slightly increased intracranial pressure displayed no significant difference of the RI within intracranial and extracranial sections of the internal carotid artery and the control group. The flow velocities, however, showed a significant increase within the intracranial segment of the internal carotid artery in comparison with the extracranial part of the internal carotid artery as well as the healthy control group. I/E-ratio for Vs increased significantly to 1.29 +/- 0.19, for Ved to 1.24 +/- 0.27 and for TAV to 1.08 +/- 0.27. Group 2 with moderately increased intracranial pressure displayed a significant increase of RI within the intracranial section of the internal carotid artery to 0.89 +/- 0.08 in comparison to the extracranial section with 0.79 +/- 0.07 and to the healthy control group with 0.75 +/- 0.07. All flow velocities decreased significantly within the intracranial section of the internal carotid artery in comparison to the extracranial part of the internal carotid artery and the healthy control group. The I/E-ratio was significantly reduced in group 2 with 0.76 +/- 0.11 for Vs, 0.38 +/- 0.21 for Ved, and 0.58 +/- 0.16 for TAV. CONCLUSION: Flow measurements in extra- and intracranial sections of the internal carotid arteries are an accurate method for semiquantitative estimation of increased intracranial pressure. This method is superior to the measurement of the RI. Slightly increased intracranial pressures below 20 cm H2O cause an increase of the I/E-ratio above 1, whereas the RI does not change. Moderately increase of the intracranial pressure above 20 cm H2O lowers the I/E-ratio significantly below normal values of 0.8, whereas the RI increases.

Blood Flow Velocity↗

PubMed2001

Association between the P12A and c1431t polymorphisms in the peroxisome proliferator activated receptor gamma (PPAR gamma) gene and type 2 diabetes.

Variation in the peroxisome proliferator-activated receptor gamma (PPAR gamma) gene may play a role in the development of type 2 diabetes mellitus. Therefore we investigated the association between the P12A and c1431t polymorphisms in the PPAR gamma gene and type 2 diabetes. The incidence of the P12A polymorphism was determined by PCR-RFLP and the c1431t by single-strand conformation polymorphism analysis in 219 patients with, and 429 without type 2 diabetes. The frequency of the A allele of P12A polymorphism was 0.16 and the t allele of c1431t polymorphism, 0.13 in patients with type 2 diabetes, and 0.13 and 0.12 respectively in subjects without diabetes 3.2% of patients with and 1.4% without type 2 diabetes were A12A. Since the polymorphisms are not linked the association of the 9 possible genotypes with type 2 diabetes was determined. All patients with genotype A12A/c1431c had type 2 diabetes (n = 3, p = 0.038). There was no association between A12A/t1431t and diabetes. DNA sequencing revealed no additional mutations in the coding region of the PPAR gamma gene in genotypes A12A/c1431c or A12A/t1431t. The associations found between polymorphisms in the PPAR gamma gene and type 2 diabetes suggest that either the A12 isofrom is functional leading to a predisposition to type 2 diabetes in homozygotes or that there is a third, unknown mutation linked to the A12/c1431 haplotype which is responsible.

Adult↗