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PubMed2002

Male fitness of oilseed rape (Brassica napus), weedy B. rapa and their F(1) hybrids when pollinating B. rapa seeds.

The likelihood that two species hybridise and backcross may depend strongly on environmental conditions, and possibly on competitive interactions between parents and hybrids. We studied the paternity of seeds produced by weedy Brassica rapa growing in mixtures with oilseed rape (B. napus) and their F(1) hybrids at different frequencies and densities. Paternity was determined by the presence of a transgene, morphology, and AFLP markers. In addition, observations of flower and pollen production, and published data on pollen fertilisation success, zygote survival, and seed germination, allowed us to estimate an expected paternity. The frequency and density of B. napus, B. rapa, and F(1) plants had a strong influence on flower, pollen, and seed production, and on the paternity of B. rapa seeds. Hybridisation and backcrossing mostly occurred at low densities and at high frequencies of B. napus and F(1), respectively. F(1) and backcross offspring were produced mainly by a few B. rapa mother plants. The observed hybridisation and backcrossing frequencies were much lower than expected from our compilation of fitness components. Our results show that the male fitness of B. rapa, B. napus, and F(1) hybrids is strongly influenced by their local frequencies, and that male fitness of F(1)hybrids, when pollinating B. rapa seeds, is low even when their female fitness (seed set) is high.

Brassica napus↗
PubMed1973

Normalization in the fitting of data by iterative methods. Application to tracer kinetics and enzyme kinetics.

1. The normalization of biochemical data to weight them appropriately for parameter estimation is considered, with reference particularly to data from tracer kinetics and enzyme kinetics. If the data are in replicate, it is recommended that the sum of squared deviations for each experimental variable at each time or concentration point is divided by the local variance at that point. 2. If there is only one observation for each variable at each sampling point, normalization may still be required if the observations cover more than one order of magnitude, but there is no absolute criterion for judging the effect of the weighting that is produced. The goodness of fit that is produced by minimizing the weighted sum of squares of deviations must be judged subjectively. It is suggested that the goodness of fit may be regarded as satisfactory if the data points are distributed uniformly on either side of the fitted curve. A chi-square test may be used to decide whether the distribution is abnormal. The proportion of the residual variance associated with points on one or other side of the fitted curve may also be taken into account, because this gives an indication of the sensitivity of the residual variance to movement of the curve away from particular data points. These criteria for judging the effect of weighting are only valid if the model equation may reasonably be expected to apply to all the data points. 3. On this basis, normalizing by dividing the deviation for each data point by the experimental observation or by the equivalent value calculated by the model equation may both be shown to produce a consistent bias for numerically small observations, the former biasing the curve towards the smallest observations, the latter tending to produce a curve that is above the numerically smaller data points. It was found that dividing each deviation by the mean of observed and calculated variable appropriate to it produces a weighting that is fairly free from bias as judged by the criteria mentioned above. This normalization factor was tested on published data from both tracer kinetics and enzyme kinetics.

Data Display↗
PubMed1986

Comparison of in-the-ear and over-the-ear hearing aid fittings.

A custom in-the-ear (ITE) hearing aid fitting was compared to two over-the-ear (OTE) hearing aid fittings for each of 9 subjects with mild to moderately severe hearing losses. Speech intelligibility via the three instruments was compared using the Speech Intelligibility Rating (SIR) test. The relationship between functional gain and coupler gain was compared for the ITE and the higher rated OTE instruments. The difference in input received at the microphone locations of the two types of hearing aids was measured for 10 different subjects and compared to the functional gain data. It was concluded that (a) for persons with mild to moderately severe hearing losses, appropriately adjusted custom ITE fittings typically yield speech intelligibility that is equal to the better OTE fitting identified in a comparative evaluation; and (b) gain prescriptions for ITE hearing aids should be adjusted to account for the high-frequency emphasis associated with in-the-concha microphone placement.

Acoustics↗
PubMed2002

On the correlation between heterozygosity and fitness in natural populations.

Three primary hypotheses currently prevail for correlations between heterozygosity at a set of molecular markers and fitness in natural populations. First, multilocus heterozygosity-fitness correlations might result from selection acting directly on the scored loci, such as at particular allozyme loci. Second, significant levels of linkage disequilibrium, as in recently bottlenecked-and-expanded populations, might cause associations between the markers and fitness loci in the local chromosomal vicinity. Third, in partially inbred populations, heterozygosity at the markers might reflect variation in the inbreeding coefficient and might associate with fitness as a result of effects of homozygosity at genome-wide distributed loci. Despite years of research, the relative importance of these hypotheses remains unclear. The screening of heterozygosity at polymorphic DNA markers offers an opportunity to resolve this issue, and relevant empirical studies have now emerged. We provide an account of the recent progress on the subject, and give suggestions on how to distinguish between the three hypotheses in future studies.

Animals↗
PubMed2003

Fitness effects of DHFR-TS mutations associated with pyrimethamine resistance in apicomplexan parasites.

Pyrimethamine resistance in the malaria parasite Plasmodium falciparum is characterized by specific point mutations in the dihydrofolate reductase (DHFR) domain of the bifunctional dihydrofolate reductase-thymidylate synthase (DHFR-TS) gene. We have previously explored the effect of these mutations by engineering homologous alleles of Toxoplasma gondii DHFR-TS, which can readily be expressed as recombinant protein for enzymatic studies, or as allelic replacements in transgenic parasites. In order to directly assess the costs of pyrimethamine-resistance in vivo, we have carried out competition studies between mixtures of T. gondii tachyzoites harbouring wild-type or mutant DHFR-TS alleles, both in tissue culture and in mice. Arg59+Asn108 mutants (using the P. falciparum numbering system) exhibit no significant fitness defects in vitro, but a fitness defect of 1.8% per generation in mice. Arg59+Ser223 mutants exhibit fitness defects of >2.8% per generation both in vitro and in vivo, which may explain why this highly pyrimethamine-resistant allele has not been observed in the field. It is important to note that long-term propagation of parasites in vitro or in vivo can produce adaptations affecting fitness by >3.7% per generation, necessitating careful attention to background in head-to-head competition studies. A sensitive PCR-based assay permits different growth rates to be assessed even in the absence of a drug resistance marker that can be scored by plaque assay.

Animals↗
PubMed2002

Fitness effects of Alternaria dauci on wild carrot in The Netherlands.

In a field experiment with a susceptible population of annual wild carrot (Daucus carota) from Iran, artificial inoculations with the fungal pathogen A. dauci led to a strong and very significant increase of the diseased leaf area. The pathogen caused a very significant decrease in fecundity and seed survival of the host. This considerable fitness reduction by A. dauci would suggest that introgression of disease resistance from cultivated (transgenic) carrot cultivars into wild carrot populations could strongly increase the fitness of wild carrot. In spite of the potential ability of A. dauci to lower the fitness of the host considerably, wild carrot is very common in The Netherlands. Disease levels of wild carrot were estimated in 26 natural populations in 1998. No A. dauci could be detected on the leaves, and only 0.4% of the seeds were contaminated with A. dauci, in spite of the conducive weather for A. dauci. Resistance tests showed that all 26 monitored populations were highly resistant to A. dauci strains from The Netherlands. It is probable that the strong potential fitness reduction by A. dauci led to a high selection pressure towards resistance in The Netherlands. In conclusion, our results suggest that transgenic resistance to A. dauci would not be beneficial to wild carrot populations in The Netherlands because they are already resistant to this pathogen.

Alternaria↗
PubMed2002

Tendon healing in a bone tunnel. Part I: Biomechanical results after biodegradable interference fit fixation in a model of anterior cruciate ligament reconstruction in sheep.

PURPOSE: Interference fit fixation of soft-tissue grafts has recently raised strong interest because it allows for anatomic graft fixation that may increase knee stability and graft isometry. Although clinical data show promising results, no data exist on how tendon healing progresses using this fixation. The purpose of the present study was to investigate anterior cruciate ligament (ACL) reconstruction biomechanically using direct tendon-to-bone interference fit fixation with biodegradable interference screws in a sheep model. TYPE OF STUDY: Animal study. METHODS: Thirty-five mature sheep underwent ACL reconstruction with an autologous Achilles tendon split graft. Grafts were directly fixed with poly-(D,L-lactide) interference screws. Animals were euthanized after 6, 9, 12, 24, and 52 weeks and standard biomechanical evaluations were performed. RESULTS: All grafts at time zero failed by pullout from the bone tunnel, whereas grafts at 6 and 9 weeks failed intraligamentously at the screw insertion site. At 24 and 52 weeks, grafts failed by osteocartilaginous avulsion. At 24 weeks, interference screws were macroscopically degraded. At 6 and 9 weeks tensile stress was only 6.8% and 9.6%, respectively, of the graft tissue at time zero. At 52 weeks, tensile stress of the reconstruction equaled 63.8% and 47.3% of the Achilles tendon graft at time zero and the native ACL, respectively. A complete restitution of anterior-posterior drawer displacement was found at 52 weeks compared with the time-zero reconstruction. CONCLUSIONS: It was found that over the whole healing period the graft fixation proved not to be the weak link of the reconstruction and that direct interference fit fixation withstands loads without motion restriction in the present animal model. The weak link during the early healing stage was the graft at its tunnel entrance site, leading to a critical decrease in mechanical properties. This finding indicates that interference fit fixation of a soft-tissue graft may additionally alter the mechanical properties of the graft in the early remodeling stage because of a possible tissue compromise at the screw insertion site. Although mechanical properties of the graft tissue had not returned to normal at 1 year compared with those at time zero, knee stability had returned to normal at that time. There was no graft pullout after 24 weeks, indicating that screw degradation does not compromise graft fixation.

Absorbable Implants↗
PubMed2001

Non-touch fittings in hospitals: a possible source of Pseudomonas aeruginosa and Legionella spp.

Non-touch fittings are gradually becoming very common in the bathrooms and toilets of public facilities and restaurants. Hospitals and other healthcare facilities have recently started to install these types of water taps to lower water consumption, thus saving costs, and to prevent healthcare workers from touching the tap, thus promoting hygiene. This study analysed the bacteriological water quality of 38 non-touch water taps in different settings in a 450-bed secondary-care hospital in Upper Austria. Two different tap types were installed: 23 taps were without temperature selection and 15 were with temperature selection (cold and warm). A membrane filtration method was used, and the authors screened for both indicator organisms and Pseudomonas aeruginosa in 100 ml water samples. In 10 non-touch taps without temperature selection, the authors also screened for Legionella spp. in 500 ml water samples. Seventy four percent of the taps without temperature selection and 7% of the taps with temperature selection showed contamination with P. aeruginosa (P<0.001). None of the taps showed contamination with indicator organisms. Detailed analysis of the source of contamination revealed that the magnetic valve and the outlet itself were heavily contaminated, whereas the junction from the central pipe system was free of contamination. All 10 analysed taps showed contamination with Legionella spp. It was concluded that the local contamination of non-touch fittings is a result of the low amount of water that flows through the outlet, the low water pressure and the column of water, which is 'still-standing' and has a temperature of about 35 degrees C, thus providing nearly ideal growth conditions for P. aeruginosa. Additionally, the presence of materials such as rubber, PVC, etc. in the fittings enhances the adhesion of P. aeruginosa and thus the production of biofilms. In conclusion, the authors wish to encourage infection control teams to evaluate the use of non-touch fittings in hospitals, especially when they are installed in risk areas.

Austria↗
PubMed2000

Comparison of fitness of two isolates of Mycobacterium tuberculosis, one of which had developed multi-drug resistance during the course of treatment.

OBJECTIVES: We report the cases of two patients, brother and sister, both with pulmonary tuberculosis. Both patients complied poorly with treatment. One developed multi-drug resistant disease, whilst the other did not. We aimed to show that the two infecting strains were the same, and then to compare the fitness of the resistant strain to that of the sensitive strain. METHODS: The isolates were typed by RFLP. The fitness of the multi-drug resistant tuberculosis strain was determined by calculating the ratio of generation produced by the drug-resistant and a drug-susceptible strain in a mixed culture. The number of bacteria present in this broth culture was estimated using the Miles and Misra technique. The number of drug-resistant bacteria present was determined by inoculating aliquots of broth onto Middlebrook 7H10 agar with 5mg/l rifampicin. RESULTS: The infecting strain of Mycobacterium tuberculosis was shown to be the same on RFLP typing in both cases. It was found that the multi-drug resistant organism had decreased fitness compared to the sensitive organism. CONCLUSION: The decreased relative fitness of the resistant strain implies a physiologic cal cost for the development of drug resistance.

Antitubercular Agents↗
PubMed2002

Press-fit versus cemented all-polyethylene patellar component: midterm results.

This study compared the midterm results between press-fit and cemented implantation of a highly congruent, all-polyethylene patellar component. We followed prospectively 172 implants (cemented, n = 133; press-fit, n = 39). Average follow up was 6 years (range, 5-8 years). Patellofemoral complications occurred in 4 cemented patellae (2.3%). Two of these patellae required revision. Cemented implants had a significantly higher incidence of patellar maltracking (30% vs 8%; P= .005). No significant differences in the overall Knee Society scores (mean, 165; SD, 27) or any of its components relevant to patellofemoral function were detected between fixation methods. A retrieved specimen showed an intervening fibrous membrane at the implant-bone interface. The potential for macrophage-mediated osteolysis at this site is unknown. No other adverse outcome was associated with press-fit implantation. These results suggest that at midterm follow-up, press-fit implantation of this all-polyethylene patellar component may improve tracking and represents a viable alternative to cement fixation.

Aged↗
PubMed2001

[Use of VR (virtual reality) software for preoperative implantation fitting with an implantable hearing aid as an example].

PURPOSE: To prove the feasibility of a preoperative fitting test for an implantable hearing aid using a VR environment. METHODS: A high-resolution spiral CT was performed after mastoidectomy in 10 temporal bone specimens. The bony structures were segmented and merged with the Computer-Aided Design (CAD) data of the hearing aid in a VR environment. For each specimen a three-dimensional fitting test was carried out by three examiners determining the implantability of the hearing aid. The implantation simulation was compared with the real implantation procedure performed by an experienced ENT surgeon. RESULTS: The used VR system enabled real-time 3D-visualisation and manipulation of CT- and CAD-data. All objects could be independently moved in all three dimensions. The VR fitting test corresponded closely with the real implantation. The implantability of the hearing aid was properly predicted by all three examiners. CONCLUSION: Merging CT and CAD data in a virtual reality environment bears high potential for the pre-surgical determination of the fit and mountability of medical implants in complex anatomical regions.

Cochlear Implantation↗
PubMed2001

Work-related injuries from mandatory fitness training among Swedish firemen.

A considerable amount of employees incur injuries in professions with mandatory on-duty fitness training. The training is necessary for maintaining a good health status, physical condition and strength in professions requiring such qualities. Injuries in Swedish firemen from on-duty fitness training between 1992 and 1998 were selected retrospectively from the Information System of Occupational Injuries (ISA) at the National Board of Occupational Safety and Health and, if having caused a sick-leave exceeding 2 weeks, to the Labour Market Insurance (AMF Insurance). The latter comprised injuries from 1995 only. During the seven-year period 1,468 injuries from fitness training occurred in male firemen. With an estimated 147 h per man and year the injury incidence was 2.6 per 10,000 h of exposure. The mean number of days of absence from work was 24.1 days (SD 39.8). In 1995, the mean cost per injury for medical treatment was close to 7,000 Euro and for production loss almost 4,500 Euro. By far the major part of the injuries, 75 %, occurred during team and contact sports (primarily floorball and soccer) and this sport category also accounted for 83% of the medical costs and 78% of the costs for production loss. It is suggested that a restriction of team and contact sports as mandatory on-duty fitness training for firemen should be tested and evaluated concerning the injury incidence.

Accidents, Occupational↗
PubMedDate not supplied

Gelastic fits in a two years old boy with a complex cerebral malformation.

We report the case of a two years old boy showing gelastic fits as the leading clinical symptom of a rare complex cerebral malformation with closed-lip schizencephaly, an arachnoid cyst and a partial agenesis of the corpus callosum. After 5 uneventful interictal electroencephalograms the patient underwent 24 h EEG with telemetry while finally presenting two laughing fits with associated spike-wave discharges in the right-centroparietal region. Medical treatment with carbamacepine was initiated and the seizure frequency decreased significantly. This is the first cited case of gelastic fits occurring in schizencephaly. In contrast to previously cited cases with laughing fits we observed a good response to anticonvulsive treatment. Moreover our patient presented a surprisingly favourable psycho-mental and motor development during an 8 months observation period.

Agenesis of Corpus Callosum↗
PubMedDate not supplied

[Axial load in case of press-fit fixation of the ACL graft--a fundamental study].

AIM: The aim of this study was the determination of the axial fixation load resting on smooth press-fit dowels needed for fixation of the patellar tendon graft (BTB) in order to reach the same fixation properties compared to the interference screw on anterior cruciate ligament (ACL) plasty. METHOD: Bovine test specimens with 27 BTB grafts fixed in tibial drill holes were used and divided in 3 groups: interference screw, and press-fit cylinder (Ø 7 mm) with 150 N and 100 N axial loads. Prior to fixation, impactation of the transplant into bone was carried out. Failure testing was done in a tensiometer at a cross-head speed of 50 mm/min. Determinations of peak load and stiffness were also made. RESULTS: Similar peak loads and stiffness were reached on introducing a press-fit dowel (slashed circle 7 mm) with 100 N and 150 N axial load compared to interference screw fixation of the BTB graft. Peak load: 988.1 N +/- 365.1 (screw) versus 1 210.4 N +/- 292.4 (dowel 150 N) and 1 109.8 N +/- 505.4 (dowel 100 N). Stiffness: 86.4 N/mm +/- 20.5 (screw) versus 102.4 N/mm +/- 15.2 (dowel 150 N) and 77.1 N/mm +/- 11.0 (dowel 100 N). There was no significant difference. CONCLUSION: When introducing a press-fit dowel (slashed circle 7 mm) with 100 N axial load into a preformed bone bed, the same fixation properties are reached as in the case of an interference screw on BTB-ACL plasty.

Animals↗
PubMed2006

[The custom-fit voice prosthesis, for treatment of periprothetic leakage after tracheoesophageal voice restoration].

BACKGROUND: Leakage around an indwelling voice prosthesis is detected during 13% up to 27% of all replacement procedures of voice prosthesis and causes serious complications in further voice restoration of the laryngectomee. Lots of therapeutic options to stop periprothetic leakage have been described (Injection of Bioplastique, autologous fat or collagen, suture techniques, spacer therapy) without convincing success rates. METHODS: Custom-fit voice prostheses are ordinary indwelling voice prostheses (Blom-Singer low pressure Indwelling 20 fr) with enlarged flanges and reduced shaft length that are individually sized for the shunt of the laryngectomee. Especially enlarging the esophageal flange provides a tight sealing of leakage around the prosthesis. PATIENTS: In a one year lasting clinical trial 692 voice prostheses were changed. In 77 cases periprothetic leakage was detected and fistulas were fitted with individually sized voice prostheses. RESULTS: In 76 cases total control of leakage was achieved without any specific complications taking place. Moreover two types of leaking tracheoesophageal fistulas were distinguished, a dilated-atrophic and an infected-necrotic type. 57% of the fistulas were dilated-atrophic type and 43% of the fistulas were classified infected-necrotic type. Infected-necrotic fistulas needed enlarged flanges tracheal an esophageal for tight sealing in 91% of the cases whereas dilated-atrophic fistulas needed double flanges only in 45%. 70% of infected-necrotic type fistulas needed only one singular history of a custom-fit prosthesis and could be changed back to ordinary indwelling prostheses after healing had taken place. CONCLUSIONS: As the insertion of a modified prosthesis is only slightly more effort than an ordinary voice prosthesis insertion, the success rate is high und complications are rare we recommend the custom-fit voice prosthesis for treatment of periprothetic leakage.

Aged↗
PubMed1994

[New aspects of hearing aid fitting].

Improved methods to diagnose a hearing loss and the enormous progress in the development of digital and programmable hearing aids have been helpful in promoting the social integration of patients, even of those affected by a profound deafness. Besides the hearing loss, recruitment effects and alteration of sound can also be compensated by the new hearing aids. However, one precondition is that the hearing aid fitting is carried out professionally, with plenty of time, and including the new hearing aid fitting methods. The new techniques developed in our hospital to optimize hearing aid fitting are pointed out. Fitting should start by considering what kind of ear mould and what kind of different modifications are to be taken. In a great number of patients we were able to verify that venting combined with the insertion of a Bakke- or Libby-horn increases not only the subjective acceptance of the hearing aid, but also significantly improves speech discrimination, particularly under background noise. The preselection of the hearing device and precise adjustment are based on the hearing loss in different frequencies, involving the principle that the frequency response of the hearing aid and the audiogram mirror each other accordingly, whereas the gain of the hearing aid can not be recognised exactly from the audiogram. In contrast to the POGO- and the NAL-method, we recommend a greater amplification, especially in the higher range of frequency. Today, the in-situ-measurement with a probe microphone is considered to be the method of choice for accurate frequency adjustment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2005

Intermolecular electrostatic energies using density fitting.

A method is presented to calculate the electron-electron and nuclear-electron intermolecular Coulomb interaction energy between two molecules by separately fitting the unperturbed molecular electron density of each monomer. This method is based on the variational Coulomb fitting method which relies on the expansion of the ab initio molecular electron density in site-centered auxiliary basis sets. By expanding the electron density of each monomer in this way the integral expressions for the intermolecular electrostatic calculations are simplified, lowering the operation count as well as the memory usage. Furthermore, this method allows the calculation of intermolecular Coulomb interactions with any level of theory from which a one-electron density matrix can be obtained. Our implementation is initially tested by calculating molecular properties with the density fitting method using three different auxiliary basis sets and comparing them to results obtained from ab initio calculations. These properties include dipoles for a series of molecules, as well as the molecular electrostatic potential and electric field for water. Subsequently, the intermolecular electrostatic energy is tested by calculating ten stationary points on the water dimer potential-energy surface. Results are presented for electron densities obtained at four different levels of theory using two different basis sets, fitted with three auxiliary basis sets. Additionally, a one-dimensional electrostatic energy surface scan is performed for four different systems (H2O dimer, Mg2+-H2O, Cu+-H2O, and n-methyl-formamide dimer). Our results show a very good agreement with ab initio calculations for all properties as well as interaction energies.

Computer Simulation↗
PubMed2006

Towards a force field based on density fitting.

Total intermolecular interaction energies are determined with a first version of the Gaussian electrostatic model (GEM-0), a force field based on a density fitting approach using s-type Gaussian functions. The total interaction energy is computed in the spirit of the sum of interacting fragment ab initio (SIBFA) force field by separately evaluating each one of its components: electrostatic (Coulomb), exchange repulsion, polarization, and charge transfer intermolecular interaction energies, in order to reproduce reference constrained space orbital variation (CSOV) energy decomposition calculations at the B3LYP/aug-cc-pVTZ level. The use of an auxiliary basis set restricted to spherical Gaussian functions facilitates the rotation of the fitted densities of rigid fragments and enables a fast and accurate density fitting evaluation of Coulomb and exchange-repulsion energy, the latter using the overlap model introduced by Wheatley and Price [Mol. Phys. 69, 50718 (1990)]. The SIBFA energy scheme for polarization and charge transfer has been implemented using the electric fields and electrostatic potentials generated by the fitted densities. GEM-0 has been tested on ten stationary points of the water dimer potential energy surface and on three water clusters (n = 16,20,64). The results show very good agreement with density functional theory calculations, reproducing the individual CSOV energy contributions for a given interaction as well as the B3LYP total interaction energies with errors below kBT at room temperature. Preliminary results for Coulomb and exchange-repulsion energies of metal cation complexes and coupled cluster singles doubles electron densities are discussed.

Algorithms↗