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F Mayer

Publications and source records attributed to F Mayer.

At least 55 records · Page 3Linked to original sources
PubMed2000

A population genetic analysis of migration: the case of the noctule bat (Nyctalus noctula).

Although rarely assessed, the population genetics of hibernating colonies can help to understand some aspects of population structure, even when samples from nursery or mating colonies are not available, or in studies of migration when both types of samples are available and can be compared. Here we illustrate both points in a survey of mitochondrial DNA (mtDNA) control region sequences used to study the population genetics of hibernating colonies of a migrating species, the noctule bat (Nyctalus noctula). Lacking samples from Scandinavian nursery colonies, we use a North European hibernacula to suggest that Scandinavian populations are isolated from Central and East European colonies. Then, we compare genetic diversities of nursery and hibernating colonies. We find a significantly higher haplotype diversity in hibernacula, confirming that they consist of individuals from different nursery colonies. Finally, we show that pairwise comparisons of the haplotype frequencies of nursery and hibernating colonies contain some information on the migration direction of the noctule bat.

Animals↗
PubMed2000

Mitochondrial DNA (mtDNA) reveals that female Bechstein's bats live in closed societies.

We present a microgeographic analysis of mitochondrial DNA (mtDNA) in Bechstein's bats using three sources of control region sequence variability, including a novel mtDNA microsatellite, to assess individual relatedness both within and among 10 maternity colonies. Comparison of marker variability among 268 adult females revealed little genetic variability within each colony. However, most colonies were clearly distinguished by colony-specific mitochondrial haplotypes (total n = 28). Low intracolony variability and strong haplotype segregation among colonies, was reflected by an extraordinary high FST of 0.68, indicating a very low intercolony dispersal rate of approximately one female in five generations. Haplotype distribution among 18 solitary males showed that males frequently disperse between colony locations, indicating the absence of dispersal barriers. Bechstein's bat maternity colonies are thus closed groups that comprise 20-40 females probably belonging to only one or, at most, two matrilines. The genetic population structure of Bechstein's bats is in agreement with the hypothesis that females seek familiar and, at least, partially related cooperation partners for raising their young. Alternatively strong philopatry might reflect the importance of profound roost or habitat knowledge for successful reproduction in female Bechstein's bats.

Animals↗
PubMed2000

Increase characteristics of the cumulated excess-CO2 and the lactate concentration during exercise.

The so-called excess-CO2 in physical exertion results stoichiometrically directly from the quantity of protons bound in bicarbonate buffering. This situation is used in determining the ventilatory threshold (VT). However, the extent to which the degree and increase characteristics of excess-CO2 can be used as an equivalent to blood lactate concentrations is uncertain. To investigate this relationship, 21 healthy men exercised on a cycle ergometer (starting at 50 watt, increases of 50 watt every 3 minutes) to subjective exhaustion. To evaluate the characteristics of this increase, a slope constant lambda was calculated in relation to performance for both the blood lactate concentration (lambda lactate) and the cumulated excess-CO2 (lambda CO2 excess). The start of the lactate increase (LT) and excess-CO2 (VT) showed good intercorrelation (VT=2.27+0.98 x LT; r=0.914; P<0.001). Mean lambda lactate and lambda CO2 excess were of similar dimensions in all subjects (69.3 +/- 39.8 watt vs. 80.11 +/- 15.7 watt), but a minority of the subjects (n=7) showed a considerably more gradual increase for the excess-CO2 to the maximum. Since in addition there was no significant correlation between the absolute values for maximum lactate concentrations and the cumulative excess-CO2, an interindividual prediction of lactate concentrations from the excess-CO2 would be difficult. It is an open question, however, whether perhaps additional performance-limiting factors, such as the ventilation or the buffering capacity, may be included when measuring the excess-CO2 so that this parameter could be more a measure for the formation rate of new lactate than the blood lactate concentration alone.

Adult↗
PubMed2000

[Limits and possibilities of 2D video analysis in evaluating physiological and pathological foot rolling motion in runners].

Three-dimensional movements of the lower extremities in support phases are usually evaluated with the help of video analysis. This analysis is mainly done two-dimensionally in a frontal and sagittal plane. Usually, the temporal ankle of the achilles tendon respectively rear foot are analysed in the frontal plane, the knee and upper ankle angle in the sagittal plane, because their values are made responsible for different sport injuries. However, so far a correlation between different injuries and biomechanical parameters could not be proven. Often, small changes in 2D video data are discussed without considering the reliability of this method of measurement. It was the aim of this study to evaluate these parameters in 2D video analyses (2D-VA) which characterize the support phases of the foot. A second goal was to find out whether a connection between these angles and chronic achillodynia can then be sensibly proven. 32 male test persons consisting of a control group (KO, n = 14) without injuries and a group with chronic achillodynia (AD, n = 18), have been examined with the test/retest method in weekly intervals. The biomechanical running analysis was done with the help of 2D-VA in the frontal and sagittal plane on a treadmill at a speed of 80% of the individual anaerobic threshold with different shoes. The test/retest variability was for all measuring points not at all satisfying. Both groups showed big mean variations in both shoes and minimal differences in the measured angles. Because of the poor capability of reproduction of the 2D-VA for angles in the frontal plane this measuring method is only usable with restrictions for the evaluation of the support phase.

Achilles Tendon↗
PubMed2000

ComP, a pilin-like protein essential for natural competence in Acinetobacter sp. Strain BD413: regulation, modification, and cellular localization.

We recently identified a pilin-like competence factor, ComP, which is essential for natural transformation of the gram-negative soil bacterium Acinetobacter sp. strain BD413. Here we demonstrate that transcription and synthesis of the pilin-like competence factor ComP are maximal in the late stationary growth phase, whereas competence is induced immediately after inoculation of a stationary-phase culture into fresh medium. Western blot analyses revealed three forms of ComP, one with an apparent molecular mass of 15 kDa, which correlates with the molecular mass deduced from the DNA sequence, one 20-kDa form, which was found to be glycosylated, and one 23-kDa form. The glycosylation of ComP was not required for its function in DNA binding and uptake. The 20-kDa form was present in the cytoplasmic membrane, the periplasm, and the outer membrane, whereas the 23-kDa form was located in the outer membrane and might be due to a further modification. Immunological data suggest that ComP is not a subunit of the pilus structures. Possible functions of ComP in the DNA transformation machinery of Acinetobacter sp. strain BD413 are discussed.

Acinetobacter calcoaceticus↗
PubMed2000

Precision of the measurements of periprosthetic bone mineral density in hips with a custom-made femoral stem.

Our aim was to determine the precision of the measurements of bone mineral density (BMD) by dual-energy x-ray absorptiometry in the proximal femur before and after implantation of an uncemented implant, with particular regard to the significance of retro- and prospective studies. We examined 60 patients to determine the difference in preoperative BMD between osteoarthritic and healthy hips. The results showed a preoperative BMD of the affected hip which was lower by a mean of 4% and by a maximum of 9% compared with the opposite side. In addition, measurements were made in the operated hip before and at ten days after operation to determine the effect of the implantation of an uncemented custom-made femoral stem. The mean increase in the BMD was 8% and the maximum was 24%. Previous retrospective studies have reported a marked loss of BMD on the operated side. The precision of double measurements using a special foot jig showed a modified coefficient of variation of 0.6% for the non-operated side in 15 patients and of 0.6% for the operated femur in 20 patients. The effect of rotation on the precision of the measurements after implantation of an uncemented femoral stem was determined in ten explanted femora and for the operated side in ten patients at 10 degrees rotation and in 20 patients at 30 degrees rotation. Rotation within 30 degrees influenced the precision in studies in vivo and in vitro by a mean of 3% and in single cases in up to 60%. Precise prediction of the degree of loss of BMD is thus only possible in prospective cross-sectional measurements, since the effect of the difference in preoperative BMD, as well as the apparent increase in BMD after implantation of an uncemented stem, is not known from retrospective studies. The DEXA method is a reliable procedure for determining periprosthetic BMD when positioning and rotation are strictly controlled.

Absorptiometry, Photon↗
PubMed2000

UFT/leucovorin plus weekly paclitaxel in the treatment of solid tumors.

The palliation of symptoms and improvement of quality of life are important aspects of therapy in patients with incurable metastatic cancer. This article describes the preliminary results of a phase I study of uracil and tegafur, an orally available fluorouracil (5-FU) derivative combined with oral leucovorin plus weekly intravenous paclitaxel. While the daily oral dose of UFT is fixed at 300 mg/m2 plus 90 mg leucovorin on days 1 to 28, paclitaxel is escalated in 10 mg/m2 steps starting with 50 mg/m2 weekly as a 1-hour infusion. To date, 26 patients with a median age of 57 years have been entered into the protocol and have received a median 2.2 cycles of therapy. Dose level 4 (paclitaxel 80 mg/m2) has been recently completed. Major dose-limiting toxicities were fatigue syndrome (two patients) and diarrhea (five patients). Preliminary responses have been observed in three of 14 currently evaluable patients. This protocol is taking the development of protracted 5-FU administration--given orally as UFT--in combination with paclitaxel one step further, using paclitaxel in a dose-dense, weekly schedule. It is hoped that an active regimen for the outpatient treatment of solid tumors will be developed.

Administration, Oral↗
PubMed1999

Male dispersal in the noctule bat (Nyctalus noctula): where are the limits?

Studying the dispersal behaviour of small, volant, and nocturnal animals such as microchiropterans with direct methods (banding--recapture, telemetry) is a very difficult task. The development of easily scorable and highly variable genetic markers nowadays allows us to study some aspects of dispersal indirectly, using population genetics. Here, we applied these indirect methods to characterize male dispersal behaviour in a European bat species. The eight microsatellite loci analysed were highly variable in all the nursing colonies assessed (h = 0.63-0.93). Contrary to what we found in the mtDNA, an AMOVA and F-statistics showed that the overall European population structure of the noctule bat was very weak, indicating a high male dispersal rate. Nevertheless, the population was not totally panmictic (theta = 0.006, p < 0.001), and neither isolation by distance, nor influence of migration could account for this result. Rather, an analysis of pairwise theta-values showed that the population structure might be explained partly by a geographical barrier to gene flow (the Alps), and partly by the fact that there is some limit to the distance the males can disperse.

Animals↗
PubMed1999

Late toxicity following curative treatment of testicular cancer.

Cisplatin appears to be the major cause for long-term toxicity in patients treated for testicular cancer. Long-term side effects consist mainly of nephrotoxicity, ototoxicity, and neurotoxicity as well as gonadal damage. Following standard-dose chemotherapy approximately 20% to 30% of patients will be affected by long-term side effects, although not all these side effects will cause an impaired quality of life. Several strategies have been or currently are being evaluated to reduce acute and long-term complications including the introduction of equally effective, but less toxic regimens, or the use of cytoprotective agents such as amifostine. Secondary acute myeloid leukemia and secondary myelodysplastic syndrome probably represent the worst possible long-term complications of cancer therapy in those patients who originally were cured of their primary testicular cancer. Therapy-related solid tumors are mainly associated with the use of radiation therapy and the risk for developing a therapy-related solid tumor is increased approximately two to three times compared to the general population. In contrast, therapy-related leukemias are predominantly associated with chemotherapy, particularly with the use of topoisomerase-II inhibitors and alkylating agents. In general, the cumulative incidence of therapy-related leukemia following treatment of germ cell cancer is low. It is approximately 0.5% and 2% at 5 years of median follow-up for patients receiving etoposide at cumulative doses< or = 2 g/m(2) and >2 g/m(2), respectively. The risk-benefit analysis in patients with testicular cancer clearly favors the use of current treatment regimens including high-dose chemotherapy. However, even the acceptably low number of therapy-related long-term complications should encourage the search for equally effective but less toxic therapies. This review will highlight important available data about therapy-related toxicity and particularly, therapy-related malignancies following cisplatin-etoposide-based chemotherapy.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1999

Principles of macromolecular organization and cell function in bacteria and archaea.

Structural organization of the cytoplasm by compartmentation is a well established fact for the eukaryotic cell. In prokaryotes, compartmentation is less obvious. Most prokaryotes do not need intracytoplasmic membranes to maintain their vital functions. This review, especially dealing with prokaryotes, will point out that compartmentation in prokaryotes is present, but not only achieved by membranes. Besides membranes, the nucleoid, multienzyme complexes and metabolons, storage granules, and cytoskeletal elements are involved in compartmentation. In this respect, the organization of the cytoplasm of prokaryotes is similar to that in the eukaryotic cell. Compartmentation influences properties of water in cells.

Archaea↗
PubMed1999

Bone mineral density of the proximal femur after unilateral cementless total hip replacement.

It was the aim of this study to examine bone mineral density changes in the non-operated contralateral femur of patients undergoing total hip replacement. Bone density in the contralateral femur of 45 patients with an average age of 54 years was measured with the aid of the DEXA technique at one week, 3 and 6 months after total hip replacement. Within the first 3 months there was an average reduction of bone density of 3.9% (3.0%-5.9%). After a further 3 months the average difference was 2.5%.

Absorptiometry, Photon↗
PubMed1999

Evolutionary adaptations of cochlear function in Jamaican mormoopid bats.

Mormoopid bat species have their echolocation system adapted to different hunting strategies. To study the corresponding mechanical properties of their inner ear, we measured distortion-product otoacoustic emissions to assess cochlear sensitivity and tuning. Mormoops blainvillii, Pteronotus macleayii and P. quadridens use frequency-modulated echolocation signals, sometimes preceded by a short narrowband signal component. Their distortion-product otoacoustic emission-threshold curves are most sensitive between 30 and 50 kHz and show no adaptation to the narrowband echolocation components. In contrast, the constant-frequency bat P. parnellii always uses long constant-frequency call components. Its inner ear is maximally sensitive at 62 kHz, the echo-frequency of the dominant constant-frequency component, and pronounced insensitivities at 61 and 93 kHz (CF2 and CF3 call frequency) are the major evolutionary change in comparison to its relatives. Furthermore, in P. parnellii, the optimum cochlear frequency separation is minimal at 62 and 93 kHz, associated with enhanced cochlear tuning, while for the other mormoopids there is no indication of enhanced tuning. The phylogeny of mormoopids, assessed by mitochondrial DNA analysis, shows a close relationship between the Pteronotus species. This suggests that major cochlear redesign, associated with the acquisition of echolocation-call specific cochlear processing in P. parnellii, has occurred within a relatively short evolutionary time scale.

Acoustic Stimulation↗
PubMed1999

[Influence of osteoarthrosis, osteoporosis, and rheumatoid arthritis at precision of osteodensitometry of lumbar spine and proximal femur].

UNLABELLED: Precision of osteodensitometric measurements using dual energy X-ray absorptiometry (DEXA) depends on various known factors, such as positioning, aortic calcification or vertebral fractures. The purpose of this study was to investigate the influence of various diseases or bone density on the reproducibility of measurements in the lumbar spine and the proximal femur. Measurements in the LWS p.a. , LWS lat. and at Ward's triangle were made in a total of 100 patients. The subjects were repositioned between measurements. In order to be able to determine the influence of various diseases, four groups of 25 patients each were formed: three with the diagnosis osteoarthrosis, osteoporosis and rheumatoid arthritis and one control group. The mean percentual difference and coefficient of variation were calculated as the measure for reproducibility. Mean percentual differences of 0.18 to 2.6% were found in the four groups at the three measurements sites. After calculation of coefficient of variation, a value between 1.2 and 2.7% was found for LWS p.a., between 7.1 and 15.7% for LWS lat. and between 4.1 and 9.9% at Ward's triangle. It was also conspicuous that the difference in coefficient of variation in osteoporosis patients was nearly double that in the control group in all measured areas. CONCLUSION: Lateral lumbar spinal measurements using DEXA cannot presently be recommended. LWS p.a. measurements and, with limitations, measurements at Ward's triangle have good precision and could be used for course documentation of bone density.

Absorptiometry, Photon↗
PubMed1999

Phosphofructokinase-1 from Saccharomyces cerevisiae: analysis of molecular structure and function by electron microscopy and self-catalysed affinity labelling.

Conventional and cryoelectron microscopy portray native octameric yeast phosphofructokinase-1 (PFK) as consisting of two identical heterotetrameric tetrahedron-like moieties being rotated relative to each other. Immunoelectron microscopy employing subunit-specific IgG identifies alpha-type subunits in the contact zone of the two tetrahedrons, while beta-chains are recognized exclusively at the tips of the octamer. The chemical reaction of phosphofructokinase with analogues of fructose 6-phosphate followed by autocatalytic phosphoryl transfer from [gamma-32P]-ATP results in a specific labelling of the alpha-subunit. AMP and fructose 2,6-bisphosphate affect labelling by stimulating the binding of substrate analogue; AMP additionally promotes phosphoryl transfer. No stimulation of labelling is observed with proteolytically modified tetrameric 12-S phosphofructokinase.

Adenosine Monophosphate↗
PubMed1999

Sensory study on the character impact odorants of roasted arabica coffee.

The potent odorants were quantified in a sample of roasted Arabica coffee. On the basis of the results, 27 odorants were dissolved in an oil/water mixture. The flavor profile of the model obtained was very close to that of the real sample. In duo and triangle tests, the model was compared with models missing one or more odorants. These experiments indicated that 2-furfurylthiol, 4-vinylguaiacol, several alkyl pyrazines, furanones, acetaldehyde, propanal, methylpropanal, and 2- and 3-methylbutanal had the greatest impact on the coffee flavor.

Adult↗
PubMed1999

Muscular fatigue, maximum strength an stress reactions of the shoulder musculature in paraplegics.

In paraplegic patients, shoulder complaints attributable to muscle dysbalances arising from the particular daily form of exercise are often observed. The goal of therapy is to correct these imbalances through muscular training, whereby eccentric exercise might offer advantages due to lower fatigue with concurrent higher maximum strength. This study therefore examines muscle fatigue, maximum strength, and suitability for paraplegics of eccentric exercise of the shoulder. Muscle fatigue, isokinetic peak torque, and EMG activity were determined eccentric (Ecc) and concentric (Con) in 41 paraplegic subjects (13 early rehabilitants; 16 trained in wheelchair sports; 12 untrained). Serum CK, myoglobin, and subjective pain were collected for one week after exercise. In eccentric exercise, there was less muscle fatigue in all groups. Highest Ecc/Con peak torque ratio was found in trained subjects in all movements, followed by the untrained and the early rehabilitants. EMG-activity was lower in eccentric compared to concentric exercise (Ecc/Con ratio <1). CK and myoglobin concentrations, like pain symptoms, showed a marked increase after exercise. It is concluded that the Ecc/Con strength patterns among paraplegics are altered. Eccentric exercise offers advantages on the basis of lower muscular fatigue independent of training status and lesion time and higher maximum strength with increasing duration of paraplegia and additional athletic training. However, due to structural damage and subjective pain eccentric exercise can only be recommended with reservations in therapy and training.

Adult↗