2,223 research outputs found
A rapid controller of temperature for use in determining Arrhenius profiles in biomembrane systems
To minimize artifacts in temperature-velocity (Arrhenius) profiles due to aging of preparations of biological membranes, a rapid controller of temperature was developed for spectrophotometric or polarographic (O 2 electrode) measurements. The reaction mixture is cooled or heated through contact with Peltier elements. One Pt temperature sensor in the cuvette or electrode holder controls current flow into the Peltier units, and another Pt temperature sensor in the reaction mixture is used to read out the sample temperature on a meter or recorder, and to provide feedback control. The sample temperature can be reproducibly set to within 0.1°C, with a noise level of 0.04°C or less; a change of 4°C takes 1 min.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44794/1/10863_2004_Article_BF00744744.pd
Louse-borne relapsing fever (Borrelia recurrentis) diagnosed in 15 refugees from northeast Africa: epidemiology and preventive control measures, Bavaria, Germany, July to October 2015
We report 15 imported louse-borne relapsing fever (LBRF) cases in refugees in Bavaria, Germany. One patient died. Epidemiological findings confirmed that all were young males from the Horn of Africa (12 from Somalia), who had similar migration routes converging in Sudan continuing through Libya and Italy. The majority likely acquired their infection during migration. Healthcare workers should be aware of LBRF in refugees passing through north Africa to ensure correct treatment and preventive measures.</jats:p
Thyroid hormone action on mitochondria
Measurements of fluorescence at >420 nm and extracted NADPH in mitochondria obtained from the livers of hypothyroid rats show that the addition of Pi, ADP and glutamate rapidly reduces over 90% of the total reducible intrinsic pyridine nucleotides in State 3, compared with 20% in normals. The total fluorescence intensity change and reducible NADP + is about twice normal in hypothyroid mitochondria. Adding 6â30 ”M l -thyroxine to hypothyroid mitochondria in vitro decreases and delays the substrate-induced reduction of pyridine nucleotides, and excludes both NADP + from such reduction and NADPH from oxidation by added ADP + Pi, without changing the high NADP(H) content. The correcting actions of the hormone are rapidly reversed by albumin, probably by binding free hormone. Changes in respiration do not appear to account for these observations. There is indirect evidence for decreased phosphorylation of added ADP in hypothyroid mitochondria, and a correction by added hormone. The hormonal actions on NADP(H) redox reactions are not reproduced by 1 to 6 ”M dinitrophenol in vitro . l -Thyroxine appears to specifically block the participation of NADP (H) in redox reactions in mitochondria from hypothyroid rats, perhaps by effecting a sequestration of the nucleotide, by inhibiting the pyridine nucleotide transhydrogenase, or by activating an energy-linked process that competes with transhydrogenation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44803/1/10863_2004_Article_BF00761448.pd
De novo backbone and sequence design of an idealized α/ÎČ-barrel protein: evidence of stable tertiary structure
We have designed, synthesized, and characterized a 216 amino acid residue
sequence encoding a putative idealized α/ÎČ-barrel protein. The
design was elaborated in two steps. First, the idealized backbone was
defined with geometric parameters representing our target fold: a central
eight parallel-stranded ÎČ-sheet surrounded by eight parallel α-helices,
connected together with short structural turns on both sides of the barrel.
An automated sequence selection algorithm, based on the dead-end elimination
theorem, was used to find the optimal amino acid sequence fitting
the target structure. A synthetic gene coding for the designed sequence
was constructed and the recombinant artificial protein was expressed in
bacteria, purified and characterized. Far-UV CD spectra with prominent
bands at 222 nm and 208 nm revealed the presence of α-helix secondary
structures (50%) in fairly good agreement with the model. A pronounced
absorption band in the near-UV CD region, arising from immobilized aromatic
side-chains, showed that the artificial protein is folded in solution.
Chemical unfolding monitored by tryptophan fluorescence revealed a
conformational stability (ÎGH_2O) of 35 kJ/mol. Thermal unfolding monitored by near-UV CD revealed a cooperative transition with an apparent T_m of 65 °C. Moreover, the artificial protein did not exhibit any affinity
for the hydrophobic fluorescent probe 1-anilinonaphthalene-8-sulfonic
acid (ANS), providing additional evidence that the artificial barrel is not
in the molten globule state, contrary to previously designed artificial a/
b-barrels. Finally, ^1H NMR spectra of the folded and unfolded proteins
provided evidence for specific interactions in the folded protein. Taken
together, the results indicate that the de novo designed α/ÎČ-barrel protein
adopts a stable three-dimensional structure in solution. These encouraging
results show that de novo design of an idealized protein structure of
more than 200 amino acid residues is now possible, from construction of
a particular backbone conformation to determination of an amino acid
sequence with an automated sequence selection algorithm
Interactions between downslope flows and a developing cold-air pool
A numerical model has been used to characterize the development of a region of enhanced cooling in an alpine valley with a width of order (Formula presented.) km, under decoupled stable conditions. The region of enhanced cooling develops largely as a region of relatively dry air which partitions the valley atmosphere dynamics into two volumes, with airflow partially trapped within the valley by a developing elevated inversion. Complex interactions between the region of enhanced cooling and the downslope flows are quantified. The cooling within the region of enhanced cooling and the elevated inversion is almost equally partitioned between radiative and dynamic effects. By the end of the simulation, the different valley atmospheric regions approach a state of thermal equilibrium with one another, though this cannot be said of the valley atmosphere and its external environment.Peer reviewe
MPAS - Ocean Simulation Quality for Variable-Resolution North American Coastal Meshes
Climate model components utilizing unstructured meshes enable variableresolution, regionally enhanced simulations within global domains. Here we investigate the relationship between mesh quality and simulation statistics using the JIGSAW unstructured meshing library and the Model for Prediction Across ScalesOcean (MPASOcean) with a focus on Gulf Stream dynamics. In the base configuration, the refined region employs 8 km cells that extend 400 km from the coast of North America. This coastal refined region is embedded within a lowresolution global domain, with cell size varying latitudinally between 30 and 60 km. The resolution transition region between the refined region and background mesh is 600 km wide. Three sensitivity tests are conducted: 1) the quality of meshes is intentionally degraded so that horizontal cells are progressively more distorted; 2) the transition region from high to low resolution is steepened; and 3) resolution of the coastal refinement region is varied from 30 km to 8 km. Overall, the ocean simulations are shown to be robust to mesh resolution and quality alterations. Meshes that are substantially degraded still produce realistic currents, with Southern Ocean transports within 0.4% and Gulf Stream transports within 12% of highquality mesh results. The narrowest transition case of 100 km did not produce any spurious effects. Refined regions with high resolution produce eddy kinetic energy and sea surface height variability that are similar to the highresolution reference simulation. These results provide heuristics for the design criteria of variableresolution climate model domains
Justifications-on-demand as a device to promote shifts of attention associated with relational thinking in elementary arithmetic
Student responses to arithmetical questions that can be solved by using arithmetical structure can serve to reveal the extent and nature of relational, as opposed to computational thinking. Here, student responses to probes which require them to justify-on-demand are analysed using a conceptual framework which highlights distinctions between different forms of attention. We analyse a number of actions observed in students in terms of forms of attention and shifts between them: in the short-term (in the moment), medium-term (over several tasks), and long-term (over a year). The main factors conditioning studentsÂŽ attention and its movement are identified and some didactical consequences are proposed
Thyroid control over biomembranes: VI. Lipids in liver mitochondria and microsomes of hypothyroid rats
The lipids of liver mitochondria prepared from normal rats and from rats made hypothyroid by thyroidectomy and injection with131INa contained similar amounts, per mg protein, of total lipids, phospholipids, neutral lipids and lipid phosphorus. Hypothyroidism caused a doubling of the relative amounts of mitochondrial cardiolipins (CL; to 20.5% of the phospholipid P) and an accompanying trend (although statistically not significant) toward decreased amounts of both phosphatidylcholines (PC) and phosphatidylserines (PS), with phosphatidylethanolamines (PE) remaining unchanged. The pattern of elevated 18â¶2 fatty acyl content and depleted 20â¶4 acyl groups of the mitochondrial phospholipids of hypothyroid preparations was reflected to varying degrees in the resolved phospholipids, with PC showing greater degrees of abnormality than PE, and CL showing none. Hypothyroidism produced the same abnormal pattern of fatty acyl distributions in liver microsomal total lipids as was found in the mitochondria. Hypothyroid rats, when killed 6 hr after injection of [1â14C] labeled linoleate, showed the following abnormalities: the liver incorporated less label into lipids, and converted 18â¶2 not exclusively to 20â¶4 (as normals do) but instead incorporated the label mainly into saturated fatty acids. These data, together with the known decrease in ÎČâoxidation, suggest that hypothyroidism involves possible defective step(s) in the conversion of 18â¶2 to 20â¶4.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142296/1/lipd0328.pd
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