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Biomedical subjects

T Schmidt

Publications and source records attributed to T Schmidt.

At least 307 records · Page 17Linked to original sources
PubMed1987

15N labeling of oligodeoxynucleotides for NMR studies of DNA-ligand interactions.

The amino protons of 15N-labeled DNA were studied as a possible structural probe in NMR investigations of the interaction of DNA with various ligands. Since the imino protons are located in the center of the double helix, and variations of their chemical shift values are difficult to interpret in terms of structural changes, these probes are not very useful. Instead, amino protons are located in the major or minor groove of the DNA and are often directly involved in the binding of a ligand. For a selective probing 4-15NH2-2'-deoxycytidine and 6-15NH2-2'-deoxyadenosine were obtained by chemical synthesis. The labeled nucleosides were introduced in distinct positions of oligodeoxynucleotides by large-scale DNA synthesis. Direct 15N NMR and 1H-15N multiple quantum NMR were applied to detect the corresponding 15N labels or protons attached to the 15N labels. Chemical shift values for the cytidine and the adenosine amino nitrogen and proton resonances of a symmetric 18 base pair lac operator sequence are reported.

Adenine↗
PubMed1987

Multilayered vesicles prepared by reverse-phase evaporation: liposome structure and optimum solute entrapment.

Liposome structure and solute entrapment in multilayered vesicles (MLVs) prepared by reverse-phase evaporation (REV) were studied. MLV-REV vesicles prepared from ether/water emulsions have high entrapment. Entrapment depends on drug, drug concentration, lipid, lipid concentration, and the container used to prepare the vesicles. By use of 300 microL of aqueous phase and 100 mg of phosphatidylcholine (PC), vesicles prepared in a test tube 25 mm X 175 mm have higher entrapment than vesicles prepared in a 100-mL round-bottom or pear-shaped flask. By use of a test tube, 100 mg of PC, and 300 microL of aqueous phase containing sucrose (1-50 mg/mL), greater than 90% sucrose entrapment was obtained. Increasing lipid content to 150 mg of PC decreased entrapment to approximately 80%. Neutral PC MLV-REV vesicles have optimum entrapment. Mixing negatively charged lipids or cholesterol (CH) with PC to make MLV-REV vesicles results in decreased entrapment compared to using only PC. Preparing vesicles with the solid lipid dipalmitoylphosphatidylcholine (DPPC) or DPPC/CH mixtures (0 less than or equal to mol % CH less than or equal to 50) results in approximately 30-40% entrapment when diethyl ether is used to make the MLV-REV emulsion. Substituting diisopropyl ether for diethyl ether and heating the MLV-REV emulsion during vesicle formation generate DPPC/CH vesicles that entrap 60% of added solutes. The high entrapment found for MLV vesicles prepared from water/organic solvent emulsions depends on maintaining a core during the process of liposome formation. A method to calculate the fraction of water residing in the liposomes' core is presented and used to compare multilayered vesicles prepared by different processes. X-ray diffraction data demonstrate that a heterogeneous distribution of lipid may exist in multilayered vesicles prepared by the REV process.

Chemical Phenomena↗
PubMed1987

Structure of an insect virus at 3.0 A resolution.

We report the first atomic resolution structure of an insect virus determined by single crystal X-ray diffraction. Black beetle virus has a bipartite RNA genome encapsulated in a single particle. The capsid contains 180 protomers arranged on a T = 3 surface lattice. The quaternary organization of the protomers is similar to that observed in the T = 3 plant virus structures. The protomers consist of a basic, crystallographically disordered amino terminus (64 residues), a beta-barrel as seen in other animal and plant virus subunits, an outer protrusion composed predominantly of beta-sheet and formed by three large insertions between strands of the barrel, and a carboxy terminal domain composed of two distorted helices lying inside the shell. The outer surfaces of quasi-threefold related protomers form trigonal pyramidyl protrusions. A cleavage site, located 44 residues from the carboxy terminus, lies within the central cavity of the protein shell. The structural motif observed in BBV (a shell composed of 180 eight-stranded antiparallel beta-barrels) is common to all nonsatellite spherical viruses whose structures have so far been solved. This highly conserved shell architecture suggests a common origin for the coat protein of spherical viruses, while the primitive genome structure of BBV suggests that this insect virus represents an early stage in the evolution of spherical viruses from cellular genes.

Biological Evolution↗
PubMed1987

[The determination of the coccidiostat nicarbazin in animal tissue and eggs. I. Determination by pulse polarography and high pressure fluid chromatography with electrochemical detection].

The determination of nicarbazin residues in foodstuffs of animal origin by two different methods, polarography, HPLC with electrochemical detection, is described. By applying pulse polarography at the dropping mercury electrode to acetonitrile extracts of animal tissues and eggs, a detection limit of 50 micrograms/kg and mean recoveries of 79% were obtained. The same extracts were used for the HPLC determination with electrochemical detection. This led to a detection limit of 1 microgram/kg. Additional rapid confirmation can be obtained from HPLC using an internal standard (nifursol) and comparing peak area proportions of both substances at varied polarization voltages. The quantitative determination of nicarbazin in chicken eggs by both polarography and HPLC was found to be in good agreement.

Animals↗
PubMed1987

Mechanisms of tumour cell metastasis.

Abercrombie and his colleagues have accumulated evidence that changes in the heterotypic contact-inhibition response are largely responsible for the invasiveness of cells, at least in culture. We have identified a 37,000 Mr protein on the surface of mouse fibrosarcoma cells that is involved in their in vitro invasion. Blocking this protein with specific antibodies inhibits the invasion of chicken heart fibroblasts by the tumour cells and normal heterotypic contact inhibition is restored. These results are presented in the general framework of metastatic mechanisms and we review a selection of more recent studies aimed at describing the metastatic phenotype in molecular terms.

Animals↗
PubMed1986

[Analysis of decay curves with biphasic kinetics].

Medication of trout and carps with chloramphenicol and sulfadimidine results in tissue residues which best fit by a biexponential decay curve. The analysis of residues does not reveal any systematic deviations of the data from the model. On the basis of this model half lives for the fast and slow drug elimination phases can be estimated. For the assessment of withdrawal times it is necessary to compute confidence limits for the decay curves. A withdrawal time may be defined by the intersection of recommended maximal concentrations with the upper confidence limit. This analysis does not include any metabolites. This model is also suited for monitoring purposes. It is recommended to apply the procedure to all chemicals exhibiting biexponential decay kinetics.

Animals↗
PubMed1986

[Support of an unusual orbital fracture by 2 balloons].

Six weeks after a traffic accident a patient presented with enophthalmos of 6 mm on the right side, a marked divergent squint, and double vision in all directions of gaze. CT scans showed a posterior medial, and inferior fracture of the orbit with tissue prolapse. In the course of surgery it became clear that an antral balloon alone would not be sufficient to push back the prolapsed tissue in the ethmoidal region. For this reason an additional, smaller (Lincoff-Kreissig) balloon was inflated in this region. The procedure was successful.

Adult↗
PubMed1986

[Case report of Möbius syndrome].

The authors describe a 5-year-old girl with congenital unilateral paralysis of the oculomotor nerve and bilateral paralysis of the facial nerve. Additionally, there was a strange innervation anomaly, which manifested as paradoxical movements of the lids in horizontal gaze movements. The case is considered to be a form of oculofacial paralysis and the findings are compared to those published in the literature.

Blepharoptosis↗
PubMed1986

Gland cells in Hydra: cell cycle kinetics and development.

The proliferative capacity of gland cells in Hydra attenuata was investigated. The results indicate that both gland cell proliferation and interstitial cell differentiation to gland cells contribute to the maintenance of the whole population. On the basis of [3H]thymidine incorporation and nuclear DNA measurements, gland cells consist of at least three different populations. One population consists of rapidly proliferating cells with a cell cycle of about 72 h. These cells are distributed throughout the body column. In the lower gastric region there is a population of non-cycling cells in G2 while in the upper gastric region there is a population of non-cycling cells in G1. About half the G1 population becomes a new antigen, SEC 1, which is typical of mucus cells.

Animals↗
PubMed1986

Upper gastrointestinal bleeding: predictors of outcome.

We reviewed the records of 115 patients treated for upper gastrointestinal (UGI) bleeding on a general surgical and trauma service from January 1981 to June 1984. Clinical variables were analyzed with regard to three outcome criteria: mortality rate, blood transfusion requirements, and need for operation. Endoscopy was performed in all patients, usually within 24 hours of detection of bleeding. Thirty-six patients required greater than or equal to 5 U of blood, 27 patients required an operation for bleeding, and 26 patients (23%) died in the hospital. In 19 patients, death was attributed to the patient's underlying disease; in seven patients, death was due to bleeding or operation. Significant predictors of death were: age greater than or equal to 60 years old (p less than or equal to 0.02), disease in three organ systems (p less than 0.05), 5 U transfusion requirement (p less than 0.001), operation for bleeding necessary (p less than 0.03), lung/liver disease (p less than 0.03), and recent stress of major operation, trauma, or sepsis. Mortality rates were highest for bleeding varices (36%) and lowest for duodenal ulcers (7.7%) and gastric ulcers (15.8%). Endoscopy accurately determined the cause of UGI bleeding in most patients. The data suggest that the unchanging mortality rate for UGI bleeding is largely due to underlying disease or injury for which the success of current treatment is limited.

Adult↗
PubMed1985

The induction of ribosome biosynthesis in a nonmitotic secretory tissue.

Many investigations of the biosynthesis of ribosomes have revealed that ribosome numbers increase with growth rate in a parallel fashion. However, we have now shown that there is also a need for active ribosome synthesis in a nonmitotic tissue which is induced to secrete. The paragonial glands of Drosophila melanogaster produce and secrete proteins that are found in the seminal fluid. Following even a single copulation event these glands are substantially reduced in size, but rapidly refill, synthesizing new secretion proteins (Chen, P.S. 1980) in Invertebrate Systems in Vitro (Kurstak, E., Maramorosch, K., and Dubendorfer, A., eds) pp. 303-313, Elsevier, Amsterdam) Anticipating that paragonial gland cells might require more ribosomes to accomplish this burst of protein synthesis, we injected 10-day-old adult male flies with either [32P] phosphate or [35S]methionine, allowed them to copulate (40 +/- 20 min after injection), and then measured the amounts of rRNA and ribosomal protein synthesis taking place with time. There is clearly a burst of ribosome synthesis starting as early as 30 min after copulation and declining after 6 h. This is evidenced by the coordinate accumulation of labeled rRNAs and ribosomal proteins. However, further experiments showed that there is no concomitant rise in the accumulation of ribosomal protein mRNAs. This suggests that these mRNAs are underutilized in the paragonial glands before copulation and more actively translated after copulation. A stimulation of translation of ribosomal proteins is then well-coordinated with increased rRNA transcription, but an increase of ribosomal protein mRNAs is not coordinated with these events. Both the up- and down-regulation of ribosome biosynthesis need not be coupled to cell growth or a specific developmental schedule, but rather may be due to the need for secretory protein synthesis.

Animals↗
PubMed1985

A new copia-like transposable element found in a Drosophila rDNA gene unit.

We have discovered a member of a new family of copia-like transposable elements inserted into the non-transcribed spacer between two ribosomal genes (rDNA). This family, which we call 3S18, consists of at least 15 elements which are scattered throughout the Drosophila melanogaster genome. The elements of this family are approximately 6.5 kb long and have 0.5 kb terminal direct repeats. All of the elements appear to have the same restriction sites. The element is mobile as the size pattern of homologous fragments varies among different strains. In situ hybridization results confirm the scattered location and transposable qualities of 3S18. The element is not transcribed into abundant RNA.

Animals↗