Search PubMed⌕ Search

Biomedical subjects

A Kohler

Publications and source records attributed to A Kohler.

At least 19 recordsLinked to original sources
PubMed2006

The genome of black cottonwood, Populus trichocarpa (Torr. & Gray).

We report the draft genome of the black cottonwood tree, Populus trichocarpa. Integration of shotgun sequence assembly with genetic mapping enabled chromosome-scale reconstruction of the genome. More than 45,000 putative protein-coding genes were identified. Analysis of the assembled genome revealed a whole-genome duplication event; about 8000 pairs of duplicated genes from that event survived in the Populus genome. A second, older duplication event is indistinguishably coincident with the divergence of the Populus and Arabidopsis lineages. Nucleotide substitution, tandem gene duplication, and gross chromosomal rearrangement appear to proceed substantially more slowly in Populus than in Arabidopsis. Populus has more protein-coding genes than Arabidopsis, ranging on average from 1.4 to 1.6 putative Populus homologs for each Arabidopsis gene. However, the relative frequency of protein domains in the two genomes is similar. Overrepresented exceptions in Populus include genes associated with lignocellulosic wall biosynthesis, meristem development, disease resistance, and metabolite transport.

Arabidopsis↗
PubMed2006

FT-IR microspectroscopy for early identification of some clinically relevant pathogens.

AIMS: To investigate the potentials and limitations of Fourier transform-infrared (FT-IR) microspectroscopy as a tool to identify, at the level of microcolonies, pathogenic bacteria frequently isolated in the clinical environment. METHODS AND RESULTS: A total of 1570 FT-IR spectra from 164 gram-positive and gram-negative bacteria isolated from patients were recorded from 6 to 10-h old microcolonies of 50-150 microm size. A classification of 100% was obtained for the most frequent gram-positive bacteria, such as Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, and Enterococcus faecium at the species level. An average accuracy of about 80% was reached with Gram negative bacteria from the Enterobacteriaceae and Pseudomonaceae families; Enterobacter aerogenes, Enterobacter cloacae, Klebsiella spp., and Citrobacter koseri; and Proteus mirabilis and Escherichia coli. Results were comparable with FT-IR measurements on dried suspensions from 18-h cultures. CONCLUSIONS: Early identification of young microcolonies is feasible with FT-IR microscopy with a very high accuracy for gram-positive bacteria. Some improvement in the transfer of microcolonies is necessary to increase the accuracy for gram-negative bacteria. SIGNIFICANCE AND IMPACT OF THE STUDY: Combination of FT-IR microscopy and multivariate data analysis could be a complementary, rapid, and reliable tool for screening and discriminating, at species and subspecies level, micro-organisms of clinical, food-borne, or environmental origins.

Animals↗
PubMed2006

Physics-based multiplicative scatter correction approaches for improving the performance of calibration models.

Light scattering effects pose a major problem in the estimation of chemical properties of particulate systems such as blood, tissue, and pharmaceutical solids. Recently, Martens et al. proposed an extended multiplicative signal correction (EMSC) approach where light-scattering effects were taken into account in an empirical manner. It is possible to include causal, first-principles mathematical models based on the physics of light scattering into the EMSC framework. This could lead to significant improvements in the separation of absorption and scattering effects. A preconditioning step prior to application of EMSC, whereby a transformation based on the physics of light scattering is used to convert the spectra into a form where the absorption and scattering effects are separable (an underlying assumption of EMSC), is proposed. Results indicate that the transformation followed by EMSC gives better calibration models than the direct application of EMSC to the absorbance spectra.

Calibration↗
PubMed2005

Extended multiplicative signal correction as a tool for separation and characterization of physical and chemical information in Fourier transform infrared microscopy images of cryo-sections of beef loin.

Extended multiplicative signal correction (EMSC) is used to separate and to characterize physical and chemical information in spectra from Fourier transform infrared (FT-IR) microscopy. This appears especially useful for applications in infrared spectroscopy where the scatter variance in spectra changes with the chemical variance in the sample set. In these cases the chemical information of specific bands that are assigned to functional groups is easier to interpret when the scatter information is removed from the spectra. We show that scatter (physical) information in FT-IR spectra of heat-treated beef loin is related to chemical changes due to heat treatment. This information is caused by textural changes induced by the heat treatment and expressed by physical effects as the optical path length. The chemical absorbance changes introduced in the FT-IR spectra due to heat treatment are shifts in the protein region of the infrared spectrum caused by changes in the secondary structure of the proteins. If the scatter and the chemical information is not separated properly, scatter information may erroneously be interpreted as chemical information.

Algorithms↗
PubMed2004

Monitoring of denaturation processes in aged beef loin by Fourier transform infrared microspectroscopy.

We present the results of a Fourier transform infrared (FT-IR) microspectroscopic study using conventional FT-IR microscopy and FT-IR imaging to detect the denaturation process during four different heating temperatures (raw, 45, 60, and 70 degrees C) spatially resolved in bovine cryosections from longissimus dorsi muscle. FT-IR imaging, employing a focal plane array detector, which allowed the simultaneous collection of spectra at 4096 pixels, enabled the investigation of the heat-induced changes in the two major meat constituents, i.e., myofibrillar and connective tissue proteins, spatially resolved. The infrared spectra of both compounds revealed that the major spectral changes involved an increase in beta-sheet and a decrease in alpha-helical structures, which appeared to be much more pronounced for the myofibers than for the connective tissue. These conformational changes could be correlated to the denaturation of the major meat proteins, such as myosin, actin, and collagen.

Animals↗
PubMed2004

Trace element carriers in combined sewer during dry and wet weather: an electron microscope investigation.

The nature of trace element carriers contained in sewage and combined sewer overflow (CSO) was investigated by TEM-EDX-Electron diffraction and SEM-EDX. During dry weather, chalcophile elements were found to accumulate in sewer sediments as early diagenetic sulfide phases. The sulfurization of some metal alloys was also evidenced. Other heavy metal carriers detected in sewage include metal alloys, some iron oxihydroxide phases and neoformed phosphate minerals such as anapaite. During rain events, the detailed characterization of individual mineral species allowed to differentiate the contributions from various specific sources. Metal plating particles, barite from automobile brake, or rare earth oxides from catalytic exhaust pipes, originate from road runoff, whereas PbSn alloys and lead carbonates are attributed to zinc-works from roofs and paint from building siding. Soil contribution can be traced by the presence of clay minerals, iron oxihydroxides, zircons and rare earth phosphates. However, the most abundant heavy metal carriers in CSO samples were the sulfide particles eroded from sewer sediments. The evolution of relative abundances of trace element carriers during a single storm event, suggests that the pollution due to the "first flush" effect principally results from the sewer stock of sulfides and previously deposited metal alloys, rather than from urban surface runoff.

Aluminum Silicates↗
PubMed2003

The role of fetal nuchal translucency and ductus venosus Doppler at 11-14 weeks of gestation in the detection of major congenital heart defects.

OBJECTIVE: To determine whether, in a selected high-risk population, Doppler velocimetry of the ductus venosus can improve the predictive capacity of increased nuchal translucency in the detection of major congenital heart defects in chromosomally normal fetuses at 11-14 weeks of gestation. METHODS: Ductus venosus Doppler ultrasound blood velocity waveforms were obtained prospectively at 11-14 weeks of gestation in 1040 consecutive singleton pregnancies. Waveforms were classified either as normal in the presence of a positive A-wave, or as abnormal if the A-wave was absent or negative. All cases were screened for chromosomal defects by a combination of maternal age and fetal nuchal translucency thickness. In 484 cases karyotyping was performed. Those fetuses found to be chromosomally normal by prenatal cytogenetic analysis, and which had abnormally increased nuchal translucency and/or abnormal ductus venosus Doppler velocimetry, underwent fetal echocardiography at 14-16 weeks of gestation. Ultrasound examination was repeated at 22-24 weeks of gestation in all women. The sensitivity, specificity and positive and negative predictive values for the detection of major cardiac defects of increased nuchal translucency thickness alone, ductus venosus Doppler alone and increased nuchal translucency thickness in association with abnormal ductus venosus Doppler were determined. RESULTS: In 29 of 998 fetuses presumed to be chromosomally normal, reversed or absent flow during atrial contraction was associated with increased (> 95(th) centile for crown-rump length) nuchal translucency. Major cardiac defects were observed in 9 of these 29 fetuses. No other major cardiac abnormalities were found in chromosomally normal fetuses in spite of the presence of either increased nuchal translucency alone or abnormal ductus venosus velocimetry. A total of 25 cardiac malformations were observed in the population. Fifteen were associated with aneuploidy and 10 fetuses had a normal karyotype. Nine of the 10 had major cardiac anomalies and one had a ventricular septal defect. The nine cases with normal karyotype and major cardiac anomalies had both increased nuchal translucency and abnormal ductus venosus flow velocity waveforms. CONCLUSION: In chromosomally normal fetuses with increased nuchal translucency, assessment of ductus venosus blood flow velocimetry could improve the predictive capacity for an underlying major cardiac defect.

Adolescent↗
PubMed2001

Parametric correlations of the energy levels of ray-splitting billiards.

Parameter-dependent statistical properties of the spectra of ray-splitting billiards are studied experimentally and theoretically. The autocorrelation functions c(x) and c(omega,x) of level velocities as well as the generalized conductance C(0) are calculated for two different classically chaotic ray-splitting billiards. Experimentally a modified Sinai ray-splitting billiard is studied consisting of a thin microwave rectangular cavity with two quarter-circle-shaped Teflon inserts. The length of the cavity serves as the experimentally adjustable parameter. For the theoretical estimates of the parametric correlations we compute the quantum spectrum of a scaling triangular ray-splitting billiard. Our experimental and numerical results are compared with each other and with the predictions of random matrix theory.

Journal Article↗
PubMed2001

[Current indications for the treatment with botulin toxin].

Botulinum toxin is more and more frequently used as a therapeutic agent. The toxin blocks selectively and reversibly the neuromuscular junction, causing a muscle relaxation. Indications are mainly muscular hypercontraction, such as dystonia, blepharospasm, focal spasticity, strabismus or tics. The range of action extend to focal hyperhydrosis, palmar, axillary or plantar. It seems now that some painful syndrome such as migraine or tension headache may benefit from toxin injections. Esthetic indications constitute an extension to the pure medical indications.

Botulinum Toxins↗
PubMed2000

Exercise test in muscle channelopathies and other muscle disorders.

We studied the percentage change in compound muscle action potential (CMAP) amplitude and area during and after a 5-min maximal contraction of the muscle. The exercise test (ET) was performed on 64 patients with different muscle disorders and on 46 normal controls. The range of normal ET values was defined as the mean + 2 SD of the control values. The mean sensitivity of the test was 63% in the whole group with ion channel muscle disorders, the highest sensitivity being seen in primary periodic paralysis (81%) and the lowest in chloride channelopathies (17%). In thyrotoxic periodic paralysis, the ET was abnormal in the three of the four patients studied. In patients with myotonic dystrophy, a smaller than normal increase in CMAP amplitude occurred during and after exercise, whereas in proximal myotonic myopathy a normal initial increase in CMAP amplitude was followed by an abnormal decrement. We conclude that the ET can be of use in confirming abnormal muscle membrane excitability in patients with calcium and sodium channelopathies and thyrotoxic periodic paralysis. In chloride channelopathy, the test may also be abnormal, but shows no, or only a small, increase in amplitude or area in the immediate postexercise period. The test may also be abnormal in proximal myotonic myopathy, but is normal in myotonic dystrophy.

Action Potentials↗
PubMed2000

Autocorrelation function of level velocities for ray-splitting billiards

We study experimentally and theoretically the autocorrelation function of level velocities c(x) and the generalized conductance C(0) for classically chaotic ray-splitting systems. Experimentally, a Sinai ray-splitting billiard was simulated by a thin microwave rectangular cavity with a quarter-circle Teflon insert. For the theoretical estimates of the autocorrelator c(x) and the conductance C(0) we made parameter-dependent quantum calculations of eigenenergies of an annular ray-splitting billiard. Our experimental and numerical results are compared to theoretical predictions of systems based on the Gaussian orthogonal ensemble in random matrix theory.

Journal Article↗
PubMed2000

Proximal myotonic myopathy: clinical, electrophysiological and pathological findings in a family.

Proximal myotonic myopathy (PROMM) is an autosomal dominant muscle disorder characterized by proximal weakness, myotonia, muscle pain and cataract. It resembles Steinert myotonic dystrophy (MD), but weakness is proximal, without facial muscle involvement, and the chromosome 19 CTG trinucleotide repeat expansion characteristic of MD is not present. We describe a further family with PROMM. Affected members complained of weakness of lower limbs or of myotonia. EMG revealed diffuse myotonic discharges. Muscle histology showed dystrophic abnormalities. The PROMM phenotype varies, even in the same pedigree, and may mimic MD or limb-girdle muscle dystrophy. EMG is particularly useful, since it may disclose myotonic discharges even in the absence of overt myotonia. Thus far it is not known whether PROMM is a single entity, or if it represents a heterogeneous group of disorders. This question will probably soon be settled through genetic analysis.

Aged↗
PubMed1999

Cerebrospinal fluid in acute peripheral facial palsy.

Cerebrospinal fluid (CSF) is rarely analyzed in peripheral facial palsy, and reports in the literature are scarce. We report the CSF findings in 265 patients with acute isolated peripheral facial palsy. The CSF findings were abnormal in 11% of 230 patients with idiopathic peripheral facial palsy, in 60% of 17 patients with Ramsay Hunt syndrome (pleocytosis), in 25% of 8 patients with Lyme disease, in all of 8 patients with HIV infection, and in 2 other patients (sarcoidosis and herpes simplex). We conclude from this large series that the CSF is usually normal in idiopathic peripheral facial palsy. If the CSF is abnormal, a specific cause should be sought.

Adolescent↗
PubMed1999

Intima-like smooth muscle cells: developmental link between endothelium and media?

The presence of non-contractile smooth muscle cells within the arterial wall raises questions as to their origin and function. These cells abound within the aortae of murine and porcine neonates, but are also present within the intimal and medial layers of adult arteries. They are largely devoid of smooth muscle-associated proteins and manifest an epithelioid form. Their morphological resemblance to endothelial cells prompted us to explore this potential relationship and to investigate their angiogenic properties in three-dimensional collagen gels. Using well-characterized smooth muscle cell lines, displaying either the intima-like (epithelioid) or media-like (spindle-shaped) morphology, we were able to show that intima-like cells share several features in common with endothelial ones and can transform into a media-like phenotype, whereby they irreversibly lose their characteristic pattern of protein expression. Intima-like, but not media-like, vascular smooth muscle cells are capable of forming capillary tubes, and, in co-cultures, can induce media-like ones to participate in this process. Such capillaries consist of a randomly-organized, mixed population of endothelial cells with intima-like or media-like smooth muscle ones. The functional significance of this diversity in smooth muscle cell type is not well understood, but phenotypic plasticity could conceivably figure as an important adaptive response to changes in the local environment.

Animals↗
PubMed1999

Test of semiclassical amplitudes for quantum ray-splitting systems.

We compute semiclassically and numerically the weights of ray-splitting orbits in the density of states of a rectangular and an annular ray-splitting billiard. The agreement between the semiclassical and the numerical results is very good, confirming the necessity of including reflection and transmission coefficients of non-Newtonian ray-splitting orbits in semiclassical expressions for the density of states of ray-splitting systems.

Journal Article↗