Biomedical subjects

I Danko

Publications and source records attributed to I Danko.

At least 55 records · Page 3Linked to original sources

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

Measurement of the lambda(+)(c) lifetime.

The Lambda+c lifetime is measured using 9.0 fb(-1) of e+e- annihilation data collected on or just below the Upsilon(4S) resonance with the CLEO II.V detector at CESR. Using an unbinned maximum likelihood fit, the Lambda+c lifetime is measured to be 179.6+/-6.9(stat)+/-4.4(syst) fs. The precision of this colliding beam measurement is comparable to other measurements, which are based on fixed-target experiments, with different systematic uncertainties.

Journal Article↗

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

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↗

PubMed2000

Study of charmless hadronic B meson decays to pseudoscalar-vector final states.

We report results of searches for charmless hadronic B meson decays to pseudoscalar( pi(+/-), K+/-, pi(0), or K(0)(S))-vector( rho, K(*), or omega) final states. By using 9.7x10(6) BB pairs collected with the CLEO detector, we report the first observation of B(-)--->pi(-)rho(0), B(0)-->pi(+/-)rho(-/+), and B(-)-->pi(-)omega, which are expected to be dominated by hadronic b-->u transitions. The measured branching fractions are (10.4(+3.3)(-3.4)+/-2.1)x10(-6), (27.6(+8.4)(-7.4)+/-4.2)x10(-6), and (11.3(+3.3)(-2.9)+/-1. 4)x10(-6), respectively. Branching fraction upper limits are set for all of the other decay modes investigated.

Journal Article↗

PubMed2000

Observation of B --> K(+/-) pi(0) and B --> (K)0 pi(0), and evidence for B --> pi(+)pi(-).

We have studied charmless hadronic decays of B mesons into two-body final states with kaons and pions and observe three new processes with the following branching fractions: beta(B-->pi(+)pi(-)) = (4.3(+1. 6)(-1.4)+/-0.5)x10(-6), beta(B-->K(0)pi(0)) = (14.6(+5.9+2.4)(-5.1-3. 3))x10(-6), and beta(B-->K(+)/-pi(0)) = (11.6(+3.0+1.4)(-2.7-1.3))x10(-6). We also update our previous measurements for the decays B-->K(+)/-pi(-/+) and B+/--->K(0)pi(+/-).

Journal Article↗

PubMed2000

Two-body B meson decays to eta and eta('): observation of B --> eta K*.

In a sample of 19 x 10(6) produced B mesons, we have observed the decays B-->eta K(*) and improved our previous measurements of B-->eta'K. The branching fractions we measure for these decay modes are B(B+-->eta K(*+)) = (26.4(+9.6)(-8.2)+/-3.3)x10(-6), B(B(0)-->eta K(*0)) = (13.8(+5.5)(-4.6)+/-1.6)x10(-6), B(B(+)-->eta'K(+) = (80(+10)(-9)+/-7)x10(-6), and B(B(0)-->eta'K0) = (89(+18)(-16)+/-9)x10(-6). We have searched with comparable sensitivity for related decays and report upper limits for these branching fractions.

Journal Article↗

PubMed2000

Measurement of charge asymmetries in charmless hadronic B meson decays.

We search for CP-violating charge asymmetries (alpha(CP)) in the B meson decays to K(+/-)pi(-/+), K(+/-)pi(0), K(0)(S)pi(+/-), K(+/-)eta('), and omega pi(+/-). Using 9.66 million upsilon(4S) decays collected with the CLEO detector, the statistical precision on alpha(CP) is in the range of +/-0.12 to +/-0.25 depending on decay mode. While CP-violating asymmetries of up to +/-0.5 are possible within the standard model, the measured asymmetries are consistent with zero in all five decay modes studied.

Journal Article↗

PubMed1998

An experimental investigation of the safe distance for internal orbital dissection.

PURPOSE: The purpose of this investigation was to determine the distance from the orbital rim to the important soft tissues of the orbital apex using eight reference points to provide clinically useful information for surgical decision making. MATERIALS AND METHODS: Eight human cadavers were used in this investigation. After circumorbital incisions were made and the canthal ligaments were detached, a careful subperiosteal dissection was performed to the soft tissues of the orbital apex. Four reference lines were established. The first two were based on a horizontal line drawn through the medial and lateral canthal ligaments and a perpendicular to this through the infraorbital foramen. The other two were created at points 45 degrees from the first two. Depth measurements were made with a straight probe at the eight points where the lines crossed the orbital rim. Means, standard deviations, and ranges were derived, and statistical differences were calculated between right and left orbits using a paired-samples t-test. Because no right and left differences were noted (P < .05), the data were pooled. RESULTS: The mean distance from the orbital rim to the soft tissues of the orbital apex was 44.1 +/- 1.4 mm medially, 38.3 +/- 3.0 mm laterally, 44.5 +/- 1.72 superiorly, and 39.4 +/- 2.9 mm inferiorly. The superomedial distance was 46.3 +/- 2.7 mm, the inferomedial distance was 44.1 +/- 1.4 mm, the inferolateral distance was 41.4 +/- 2.5 mm, and superolateral distance was 39.4 +/- 2.8 mm. CONCLUSIONS: The distances from the orbital rim to the soft tissues of the orbital apex varied among the eight different reference points (range, 38.3 +/- 3.0 mm to 46.3 +/- 2.7 mm). No distance was less than 31.0 mm or exceeded 51.1 mm. There was no difference noted (P < .05) between the right and left sides for each of the corresponding reference points.

Blindness↗

PubMed1998

The efficient expression of intravascularly delivered DNA in rat muscle.

Previous studies have demonstrated that muscle can take up and express naked DNA or RNA. This study demonstrates that the pDNA can be delivered to and expressed within skeletal muscle when injected rapidly, in a large volume and when all blood vessels leading into and out of the hindlimb are occluded. The additional use of collagenase, papaverine and ischemia raised expression moderately but was not critical. These results demonstrate that a nonviral method can lead to high levels of expression in the muscles of adult animals large than mice.

Animals↗

PubMed1997

High expression of naked plasmid DNA in muscles of young rodents.

There is a time window at 2 weeks of age for achieving very high levels of foreign gene expression from the intramuscular injection of naked plasmid DNA in mice and rats. The highest expression, over 1 microg of luciferase protein/muscle, was obtained in Balb/C mice using constructs containing the CMV promoter, a chimeric intron and the luc+ luciferase gene. Approximately 50% of the myofibers were intensely blue following the intramuscular injection of a beta-galactosidase expression vector in 2 week old Balb/C mice. The effects of age, mouse strain and construct were multiplicative, resulting in >1000-fold greater luciferase and approximately 20-fold more beta-galactosidase-positive cells. These high levels of expression were unstable and were not observed in larger animals (dog, rhesus monkey). These results indicate that enormous levels of foreign gene expression can be obtained in muscle with naked DNA in vivo and will enable the temporary effects of gene function and expression in rodent muscle to be expeditiously studied.

Age Factors↗

PubMed1995

A plasmid-based self-amplifying Sindbis virus vector.

Sindbis virus was used as a self-amplifying eukaryotic expression vector. A recombinant cDNA genome of this (+)-strand RNA virus was placed under the transcriptional control of a Rous sarcoma virus LTR (RSV) promoter. Transfection of this plasmid construct into mammalian cell lines (3T3, HepG2, and 293 cells) resulted in expression of the luciferase reporter gene. High-expression levels were also measured after transfection into primary rat myoblasts. In differentiated myotubes, expression levels generated by the Sindbis virus vector were up to 200 times higher than those obtained with a conventional RSV expression vector. In vivo expression was detected after injection of plasmid DNA into mouse quadriceps. In vivo expression was transient and undetectable by day 16. This self-amplifying expression vector can be used for generating high-level expression of transgenes in vitro and in vivo. Its transient nature in vivo could allow for safe, short-term delivery of gene products in gene therapy protocols. It should facilitate the study of Sindbis and other RNA viruses.

3T3 Cells↗

PubMed1995

Expression of deletion-containing dystrophins in mdx muscle: implications for gene therapy and dystrophin function.

The expression of full-length dystrophin and various dystrophin deletion mutants was monitored in mdx mouse muscle after intramuscular injection of dystrophin-encoding plasmid DNAs. Recombinant dystrophin proteins, including those lacking either the amino terminus, carboxyl terminus, or most of the central rod domain, showed localization to the plasma membrane. This suggests that there are multiple attachment sites for dystrophin to the plasma membrane. Only those constructs containing the carboxyl terminus were able to stabilize dystrophin-associated proteins (DAP) at the membrane, consistent with other studies that suggest that this domain is critical to DAP binding. Colocalization with DAP was not necessary for membrane localization of the various dystrophin molecules. However, stabilization and co-localization of the DAP did seem to be a prerequisite for expression and/or stabilization of mutant dystrophins beyond 1 wk and these same criteria seemed important for mitigating the histopathological consequences of dystrophin deficiency.

Animals↗

PubMed1994

Direct gene transfer into muscle.

Gene therapy has great promise for the treatment and the prevention of a broad range of inherited and acquired diseases. Gene transfer methods currently explored include the use of viral vectors and physical-chemical methods. Plasmid DNA can be taken up by skeletal muscle cells in vivo without any special delivery mechanism and persist long-term in an extrachromosomal, non-replicative circular form. Thus, foreign genes can be expressed permanently in skeletal muscle. At present the efficiency of gene transfer is not high enough to treat genetic muscle diseases. However, even at the relatively low efficiency of expression we are able to achieve at present, plasmid DNA transfer seems to be a very promising way of programming cells in vivo to secrete proteins for immunization purposes.

Animals↗

PubMed1994

Pharmacological enhancement of in vivo foreign gene expression in muscle.

Intramuscular injection of naked plasmid DNA provides a means for gene transfer and expression in striated muscle. In this study, the effects of treating muscle with normal saline, etidocaine, mepivacaine, acetic anhydride, sodium bicarbonate, Notechis scutatus venom, cardiotoxin and bupivacaine before plasmid DNA injection on foreign gene expression were evaluated. Dose dependence, strain and species specificity, the time interval between pharmacological agent and plasmid DNA injection, the stability of gene expression and the fate of the injected plasmid DNA were studied using reporter gene expression, by histological examination and semi-quantitative polymerase chain reaction. Of the various agents tested, the best enhancement of foreign gene expression occurred in muscle treated with 0.75% bupivacaine five to seven days before plasmid DNA injection. Rat and mouse quadriceps muscle treated with 0.75% bupivacaine had levels of luciferase activity four- to 40-times greater than non-bupivacaine-treated muscle. Also, beta-galactosidase expressing myofibers were observed throughout the length of the muscle in samples treated with 0.75% bupivacaine before reporter gene injection. Muscle treated with 0.75% bupivacaine fully recovered from the degeneration caused by its injection with no long-term effects histologically. The heightened level of reporter gene expression persisted in 0.75% bupivacaine-treated muscle for one month, but decreased to that of non-bupivacaine-treated muscle by two months after plasmid DNA injection. Enhancement of foreign gene expression may be particularly advantageous in vaccination protocols employing intramuscular plasmid injection.

Acetic Anhydrides↗

PubMed1993

Dystrophin expression improves myofiber survival in mdx muscle following intramuscular plasmid DNA injection.

Expression of Becker-like and full-length human dystrophins was stable for at least 6 months in mdx mouse muscle following intramuscular plasmid DNA injection. Intramuscular injection of a single plasmid DNA encoding both luciferase and dystrophin resulted in stable luciferase expression for at least 2 months in mdx muscle, whereas injection of plasmid DNA encoding only luciferase did not result in stable luciferase expression. These results suggest that expression of either full-length or Becker-like dystrophins protects mdx mouse myofibers from degeneration.

Animals↗

PubMed1992

The frequency of revertants in mdx mouse genetic models for Duchenne muscular dystrophy.

The mdx mouse has been used for the development of cellular and gene therapies for Duchenne muscular dystrophy. The relatively frequent occurrence of dystrophin-positive muscle cells called revertants has hampered these efforts by interfering with data interpretation. The mdx4cv and mdx5cv dystrophin mouse mutants have approximately 10-fold fewer revertants than the mdx mutant at both 2 and 6 mo. The mdx3cv dystrophin mouse mutant may be a useful model for some types of human dystrophin deficiencies in which the levels of dystrophin are low but not completely absent.

Animals↗