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Biomedical subjects

D Zink

Publications and source records attributed to D Zink.

At least 37 records · Page 2Linked to original sources
PubMed1997

Usefulness of respiratory gated magnetic resonance coronary angiography in assessing narrowings > or = 50% in diameter in native coronary arteries and in aortocoronary bypass conduits.

Magnetic resonance coronary angiography (MRCA) is a promising method for the assessment of proximal coronary artery stenosis. Conventional 2-dimensional techniques require repetitive breath holds to image multiple sections. This may lead to misregistrations if the respiratory level is not exactly reproduced. In the present study, MRCA was performed using a 3-dimensional approach with navigator echo-based respiratory gating. In 73 patients (55 men and 18 women) who were referred for cardiac catheterization, the assessment of significant stenoses (> or = 50%) was performed in the proximal and midsegments of the coronary arteries after multiplanar reconstruction of the visualized coronary arteries. In addition, in 8 patients with coronary artery bypass grafts the patency of the transplants was evaluated. After withdrawing 8 patients from analysis because of poor image quality, stenosis evaluation was possible in 236 of 455 reviewed coronary segments (52%). In the other 219 cases, either the visualization of the vessel segment was indistinct (30%) or the segment was located outside the imaging volume (18%). In total, 28 of 43 significant coronary stenoses could be correctly identified (65%). Evaluation of bypass graft patency was possible in 7 patients. All 4 occluded and 13 of 15 patent grafts were correctly classified. Thus, respiratory gated MRCA is a feasable method for the assessment of hemodynamically significant coronary stenoses and bypass graft patency. However, technical improvements are mandatory to improve accuracy of the method.

Adult↗
PubMed1997

Illudinic acid, a novel illudane sesquiterpene antibiotic.

A novel illudane sesquiterpene antibiotic (1) with activity against methicillin-resistant Staphylococcus aureus (MRSA), has been isolated. Its MIC against MRSA was found to be 16 micrograms/mL. It also shows L-1210 cytotoxicity with an IC50 of 10-15 micrograms/mL.

Animals↗
PubMed1997

Visualization of the coronary arteries in three-dimensional reconstructions using respiratory gated magnetic resonance imaging.

OBJECTIVE: To assess the applicability of respiratory-gated magnetic resonance coronary angiography, combined with three-dimensional image reconstruction, for visualizing the coronary arteries. METHODS: Twenty subjects (three healthy volunteers and 17 patients without stenoses detected by coronary angiography) were investigated. Magnetic resonance imaging was performed in a 1.5 T scanner using ECG-triggered gradient-echo sequences to acquire a volume data set consisting of 24-48 contiguous axial cross-sections of the heart (2 mm slice thickness, 1.17 mm x 1.17 mm in-plane resolution). Navigator-echo-based retrospective respiratory gating was used to minimize respiratory motion artifacts. Three-dimensional reconstructions of the heart were rendered using surface-display techniques. The length of the visualized coronary arteries was measured in curved multiplanar reconstructions. RESULTS: In the three-dimensional reconstructions, the left main artery (LMA) and left anterior descending artery (LADA) were visualized in 17 cases, the left circumflex artery (LCXA) in 15, and the right coronary artery (RCA) in 16 cases. Vessel continuity was uninterrupted in all 17 cases for the LMA, in 14 for the LADA, eight for the LCXA, and 13 for the RCA. The mean lengths of the visualized vessels were 14 +/- 7 mm for the LMA, 65 +/- 13 mm for the LADA, 45 +/- 16 mm for the LCXA, and 37 +/- 26 mm for the RCA. Reasons for impaired visibility of the LCXA and RCA were poor image quality due to there being a low contrast:noise ratio, motion artifacts, and incomplete coverage by the imaging volume. CONCLUSIONS: Navigator-echo-based magnetic resonance imaging is a promising technique for investigating the coronary arteries. Acquisition of a volume data set permits three-dimensional displays of the coronary vessels.

Case-Control Studies↗
PubMed1997

Platelet activation in embolic and preembolic status of patients with nonrheumatic atrial fibrillation.

STUDY OBJECTIVE: Information on platelet activation possibly associated with a preembolic or embolic status in nonrheumatic atrial fibrillation (AF) with special regard to the role of platelet membrane activation markers (P-selectin and CD63). STUDY POPULATION: The study included 60 patients with nonrheumatic AF; 28 of them had a history of an embolic event. The age-matched control group consisted of 28 healthy subjects (13 men and 15 women). INTERVENTIONS: Patients underwent transesophageal echocardiography to detect eventual intracardiac thrombus or spontaneous echo contrast that would represent a preembolic status. Blood samples were taken from all persons to evaluate markers for platelet activation under these conditions. RESULTS: Measurements of hematologic variables did not differ significantly between normal subjects and patients presenting with AF but no preembolic or embolic status. Elevated concentrations of fibrinogen were significantly related to the presence of left atrial spontaneous echo contrast. The amount of circulating platelets expressing P-selectin and CD63 was significantly higher in the patients positive for both spontaneous echo contrast and left atrial thrombus or embolic events. Furthermore, in these groups, significantly more leukocyte-platelet conjugates were present. CONCLUSION: Platelet activation indicated by platelet membrane activation markers occurs in embolic and preembolic status of patients with nonrheumatic AF.

Aged↗
PubMed1995

Drosophila Polycomb-group regulated chromatin inhibits the accessibility of a trans-activator to its target DNA.

The genes of the Polycomb-group (Pc-G) are responsible for maintaining the inactive expression state of homeotic genes. They act through specific cis-regulatory DNA elements termed PREs (Pc-G Response Elements). Multimeric complexes containing the Pc-G proteins are thought to induce heterochromatin-like structures, which stably and heritably inactivate transcription. We have tested the functional role of the FAB fragment, a PRE of the bithorax complex. We find that this element behaves as an orientation dependent silencer, capable of inducing mosaic gene expression on neighboring genes. Transgenic fly lines were constructed containing a PRE adjacent to a reporter gene inducible by the yeast GAL4 trans-activator. The competition between the activator and Pc-G-containing chromatin was visualized on polytene chromosomes using immunocytochemistry. The Pc-G protein Polycomb and GAL4 have mutually exclusive binding patterns, supporting the notion that Pc-G-induced chromatin structures can prevent activators from binding to their target sequences. However, this antagonistic function can be overcome by high doses of GAL4, even in the absence of DNA replication.

Animals↗
PubMed1995

Genetic determinants of sense organ identity in Drosophila: regulatory interactions between cut and poxn.

Two genes involved in defining the type of sense organ have been identified in Drosophila. The gene cut differentiates the external sense organs (where it is expressed) from the chordotonal organs (where it is not); among the external sense organs poxn differentiates the poly-innervated organs (where it is expressed) from the mono-innervated organs (where it is not). Here we show that the expression of poxn in normal embryos does not depend on cut, and that poxn is capable of inducing the expression of cut. We have identified a small domain of the very large cut regulatory region as a likely target for activation by poxn.

Animals↗
PubMed1992

Polycomb and polyhomeotic are constituents of a multimeric protein complex in chromatin of Drosophila melanogaster.

The polycomb group (Pc-G) genes are responsible for maintaining the repressed state of homeotic genes during development. It has been suggested that the Pc-G exerts its transcriptional control by regulating higher order chromatin structure. In particular, the finding of genetic and molecular similarities to components involved in heterochromatin formation, led to the proposal that homeotic genes are permanently repressed by mechanisms similar to those responsible for heterochromatin compaction. Because of synergistic effects, Pc-G gene products are thought to act in a multimeric complex. Using immunoprecipitation we show that two members of the Pc-G, Polycomb and polyhomeotic, are constituents of a soluble multimeric protein complex. Size fractionation indicates that a large portion of the two proteins are found in a distinct complex of molecular weight 2-5 x 10(6) Da. During embryogenesis the two proteins show the same spatial distribution. In addition, by double-immunofluorescence labelling we can demonstrate that Polycomb and polyhomeotic have exactly the same binding patterns on polytene chromosomes of larval salivary glands. We propose that some Pc-G proteins act in multimeric complexes to compact the chromatin of stably repressed genes like the homeotic regulators.

Animals↗
PubMed1992

A novel inositol mono-phosphatase inhibitor from Memnoniella echinata. Producing organism, fermentation, isolation, physicochemical and in vitro biological properties.

A novel inositol mono-phosphatase inhibitor, L-671,776 (1), was discovered from a culture of the hyphomycete, Memnoniella echinata (ATCC 20928). 1 has a molecular weight of 388 and a molecular formula of C23H32O5. The mode of inhibition is non-competitive, with a Ki of 450 microM. It shows no inhibition of myo-inositol 1,4-bisphosphate 1-phosphatase or myo-inositol 1,4,5-triphosphate 5-phosphatase, although it weakly inhibits myo-inositol 1,4,5-triphosphate 3-kinase (IC50 = 3 mM). It elevates inositol monophosphates in rat parotid slices (EC50 approximately 3 mM), but abolishes agonist effects. It also produces short-lived contraction of guinea pig trachea at 300 microM.

Animals↗
PubMed1992

Cochinmicins, novel and potent cyclodepsipeptide endothelin antagonists from a Microbispora sp. II. Structure determination.

Cochinmicins I, II, and III are competitive endothelin antagonists produced by Microbispora sp. ATCC 55140. The cochinmicins are cyclic depsipeptides containing six alpha-amino acids and a pyrrolecarboxylic acid. Based upon MS, 1D and 2D NMR, and LC data, the structures and absolute stereochemistries of the cochinmicins have been assigned. All three components have the same basic sequence and contain one equivalent each of D-allo-threonine, D-alanine, L-phenylalanine, D-phenylalanine, 5-chloropyrrole-2-carboxylic acid (or pyrrole-2-carboxylic acid in cochinmicin I), plus two equivalents of 3,5-dihydroxyphenylglycine (DHPG). The phenylalanine residues were differentiated via a methanolysis product which contained only one of the phenylalanine residues. Both DHPG residues have the D configuration in the more active cochinmicins I and III. Cochinmicin II contains both D- and L-DHPG and these residues have been differentiated in the sequence based upon 1H NMR data.

Amino Acid Sequence↗
PubMed1992

L-696,474, a novel cytochalasin as an inhibitor of HIV-1 protease. II. Isolation and structure.

A novel HIV-1 protease inhibitor, L-696,474 (C30H39NO4, 477), was isolated from the fermentations of the fungus Hypoxylon fragiforme (ATCC 20995, MF5511) and purified by silica gel chromatography followed by crystallization. Spectroscopic studies have shown the competitive inhibitor L-696,474 to be a novel cytochalasin. Two related novel cytochalasins were also isolated and had no effect on the enzyme.

Ascomycota↗
PubMed1991

Predicting outcome of care in the neonatal intensive care unit.

The accuracy of a neonatal intensive care unit (NICU) staff in predicting the outcome and length of stay of infants admitted to the NICU, and the factors they felt were important in making these predictions, were evaluated. This prospective study used a questionnaire to survey 44 nurses, residents, and attending neonatologists working in the NICU about the predicted outcomes of 52 infants admitted to the NICU at the University of Nebraska Medical Center over a 1-month period. Factors previously identified by the staff as important indicators of infant outcome were assigned points of importance by the respondents, and specific values for these factors were recorded for each infant. The NICU staff indicated that gestational age was the most important indicator of infant outcome. The attending neonatologists placed more value on gestational age (analysis of variance [ANOVA] P less than .0001) than did the nurses or residents. Among the staff groups, there were significant differences in the weight or points assigned to a given factor for pulmonary function, renal function, number of resuscitations, and the "other" category (ANOVA P less than .05). The nurses ranked pulmonary function criteria lower than the residents did (P less than .04), but considered renal function more important than either the residents (P = .005) or the attending neonatologists considered it to be (P = .01). The number of resuscitations was ranked higher by the nursing staff than by other groups, whereas the attending neonatologists assigned less importance to the "other" category.(ABSTRACT TRUNCATED AT 250 WORDS)

Forecasting↗
PubMed1989

Directed biosynthesis of avermectins.

Avermectin homologs are produced by Streptomyces avermitilis when externally supplied with sodium 2-methylpentanoate and sodium 2-methylhexanoate. The homologs carry 2-pentyl and 2-hexyl groups, respectively, at C-25 of the aglycone moiety as opposed to the 2-butyl group of "a" components and the isopropyl group of "b" components of natural avermectins. The new homologs designated as avermectin "c" and "d" components, respectively, possess potent anthelmintic and insecticidal activity.

Animals↗