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Biomedical subjects

F Eggert

Publications and source records attributed to F Eggert.

At least 19 recordsLinked to original sources
PubMed1999

In vitro investigation of the liberation of fluoride ions from toothpaste compounds in a permeation model.

The most important requirement for effective topical fluoride prophylaxis from toothpaste containing fluoride is that the active fluoride agent must be chemically free, and the rapid spread of the dissolved fluoride ions over the tooth surface. Abrasive compounds in the toothpastes and the brief residence time at the site of action, the oral cavity and tooth surface must not prevent the liberation. Using a two-chamber diffusion cell and an ion-selective fluoride electrode, the content of fluoride ions in five different fluoride-containing toothpastes was determined by direct potentiometry as a function of time and the different abrasive compounds employed. The investigation has demonstrated that a reduction of the release rate of fluoride ions by nearly 50% is seen when calcium carbonate and calcium hydrogen phosphate dihydrate are used as abrasive compounds and combined with sodium fluoride.

Fluorides↗
PubMed1998

High-Resolution X-ray Spectroscopy Close to Room Temperature.

: Originally designed as position-sensitive detectors for particle tracking, silicon drift detectors (SDDs) are now used for high-count rate X-ray spectroscopy, operating close to room temperature. Their low-capacitance read-node concept places them among the fastest high-resolution detector systems. They have been used in a new spectrum of experiments in the wide field of X-ray spectroscopy: fluorescent analysis, diffractometry, materials analysis, and synchrotron experiments such as X-ray holography and element imaging in scanning electron microscopes. The fact that the detector system can be used at room temperature with good spectroscopic performance and at -10 degrees C with excellent energy resolution, avoiding liquid nitrogen for cooling and high-quality vacuum, guarantees a large variety of new applications, independent of the laboratory environment. A brief description of the device principles is followed by basics on low noise amplification. The performance results of a complete detector system are presented as well as some dedicated applications already realized, including use in a surface mapping instrument and use of a "mini-spectrometer" for the analysis of works of art. Fully depleted pn-charge-coupled devices (pn-CCDs) have been fabricated for the European X-ray Multi-Mirror mission (XMM) and the German X-ray satellite ABRIXAS, enabling high-speed, low-noise, position-resolving X-ray spectroscopy. The detector was designed and fabricated with a homogeneously sensitive area of 36 cm2. At -70 degrees C it has a noise of 4 e- rms, with a readout time of the total focal plane array of 4 msec. The maximum count rate for single photon counting was 10(5) cps under flat field conditions. In the integration mode, more than 10(9) cps can be detected at 6 keV. Its position resolution is on the order of 100 µm. The quantum efficiency is higher than 90%, ranging from carbon K X-rays (277 eV) up to 10 keV.

Journal Article↗
PubMed1998

Pathophysiologically correlated deficits of information processing in obstructive sleep apnea patients.

In obstructive sleep apnea patients, who intermittently stop breathing at night for some seconds, functions of vigilance and attention seem to be impaired. The aim of our study was to investigate if nocturnal hypoxia as one possible detrimental factor is associated with the degree of modality shift effect expressing attention function at a very basic level of information processing. For the first time an experimental approach was applied to examine attention deficits in sleep apnea patients. Correlation analyses between pathophysiological parameters and attention function revealed a stronger association for the modality shift effect than for simple reaction times.

Cognition Disorders↗
PubMed1997

Fractionation and bioassay of human odor types.

Human urine samples were fractionated to examine the contribution of volatiles to the individual body odor. The samples were obtained from 4 male donors and fractionated using a vacuum technique. The volatiles from the chemical fractions were analyzed using the CLSA technique and gas chromatography. Thereafter, these fractions were tested in a computer-controlled olfactometer by trained rats. Although the rats were able to discriminate the distillation residue, they could not recognize the urine odor in the distilled fraction. The results of gas chromatography indicate a continuous release of volatile constituents in the distillation residue.

Adult↗
PubMed1997

MHC and behavior.

Explore the source record for details and available documents.

Behavior↗
PubMed1996

MHC-associated and MHC-independent urinary chemosignals in mice.

The chemosensory identity of mice, rats, and humans is determined partly by polymorphic genes of the major histocompatibility complex (MHC). In inbred strains of mice as well as in seminatural populations MHC-associated mating preferences selectively influence reproductive success. To explore MHC-associated chemosignals in relation to otherwise genetically determined chemosignals a first study was conducted on seven trained rats' responses to the odors of inbred strains of mice. Results of the first study confirmed that neither the MHC nor genes in the genetic background dominate in determining urine odor specificity of mice and that specific olfactory cues associated with either the MHC or the genetic background can be identified by olfaction. In a second study, these specific olfactory cues were analyzed by means of gas chromatography. The results indicate that specific volatile components associated with either the MHC or the genetic background can be found in mouse urine odor, and that profiles of ubiquitous volatile components show some association with either the MHC or the genetic background. Furthermore, results show that a small number of specific compounds as well as a profile of some few ubiquitous volatiles constitute MHC-associated odor cues and that influences of the MHC and genes in the genetic background interact in constituting urine odor specificity in mice.

Animals↗
PubMed1996

[Assessment of attention parameters in sleep apnea patients].

In the current study the modality-shift paradigm was applied to examine attention deficits in sleep-apnea patients. The reaction times of ipsi- and crossmodal light and sound stimuli were measured on 34 patients presenting symptoms of sleep-apnea. Some of the simple reaction times of ipsimodal (light-light; sound-sound) and crossmodal (light-sound; sound-light) stimuli correlated with mean or with minimal oxygen saturation, but did not correlate with the frequency or duration of obstructive apneas and hypopneas. However, results are different if the amount of modality-shift effect is taken into consideration. Significant correlations were found for the maximal duration of obstructive apneas and hypopneas as well as for mean oxygen saturation.

Attention↗
PubMed1994

MHC-associated and MHC-independent urinary chemosignals in mice are expressed via the hematopoietic system.

The change in genetically determined urine odors which appears after experimental bone marrow transplantations in mice was examined in order to test whether the HMC is the only group of genes that influences the chemosensory identity via the hematopoietic system. 5 female rats were trained in a computer-controlled olfactometer to discriminate urine odors of two MHC congenic or background congenic inbred strains of mice. Transfer-of-training tests with urine samples of irradiated mice which were restored with bone marrow either from an MHC congenic or a background congenic inbred strain reveal a change of urinary chemosignals after both types of experimental bone marrow transplantation. Thus, both MHC-associated as well as MHC-independent urinary chemosignals are expressed via the hematopoietic system.

Animals↗
PubMed1994

[Postoperative behavior of gastrectomized rats in an open field after Roux-Y-reconstruction with and without pouch].

In a series of experimental studies on rat behavior following reconstructive surgery after gastrectomy the effects of Roux-Y-Pouch-technique (RY-P) as compared to Roux-Y (RY) alone were observed. 12 rats with RY-P and 13 rats with RY were tested on days 100-105 post surgery using the Open-Field-test paradigm. Feeding behavior and weight were additionally controlled. Data analysis of repeated measurement design (ANOVA) revealed significant group x time-interaction between type of reconstruction and exploratory behaviors (p < .01). Moreover, RY-P rats consumed more food (p < .001), had higher weight gain (p < .01), and tended to more normal defecation. Overall, results favour the more physiological type of reconstruction.

Anastomosis, Roux-en-Y↗
PubMed1993

The hematopoietic system influences odor specificity in mice and rats.

The change in strain-specific urine odors which appears after bone marrow transplantations was examined in mice and rats in order to demonstrate an influence of the hematopoietic system on urinary chemosignals. Four rats were trained in an olfactometer to discriminate two allogeneic mouse or rat strains via their urine odors. Urine samples obtained from two inbred strains of mice, from two inbred strains of rats, from allogeneic reconstituted mice, and from semiallogeneic reconstituted rats were combined in a number of 'transfer of training' tests. Results confirm findings that the hematopoietic system influences odor specificity in mice. For the first time a change of urinary chemosignals after bone marrow transplantation in rats was demonstrated by using semiallogeneic reconstituted rat chimeras.

Animals↗
PubMed1992

[Characteristics of changes of personal odor after experimental bone marrow transplantation].

In an operant conditioning paradigm 4 Balb/c inbred strain mice were conditioned to discriminate between urine samples of two other inbred strains. The purpose was to examine whether or not the known stimulus configuration during training had any effect upon the rate of recognition of other stimuli. On the basis of this procedure, we subsequently investigated the extent to which an allogeneic bone marrow transplantation interferes with the olfactory identity of an individual. For the transplants a strain was inbred which had no contact to the animals tested, a procedure used for the first time here. Furthermore, also for the first time, it was possible to demonstrate in a direct comparison, the role played by donor versus recipient characteristics on the olfactory composition of the recipients odor.

Animals↗
PubMed1989

Changes in strain-specific urine odors of mice due to bone marrow transplantations.

The change in strain-specific urine odors which appears after bone marrow transplantations was systematically examined in mice in order to demonstrate an influence of the hematopoietic system on urinary chemo-signals. Four mice were trained in a Y maze to discriminate two fully allogeneic mouse strains via their urine odors. Urine samples obtained from three inbred strains, from syngeneic reconstituted mice, and from allogeneic reconstituted chimeras were combined in a number of 'transfer of training' tests. The strain-specific urine odors of the recipients were changed by a fully allogeneic bone marrow transplant. Since this change could not be found in syngeneic reconstituted mice, we concluded that it was caused by the graft. Experiments partly failed to demonstrate donor- and recipient-specific components in the urine odor of the chimeras.

Animals↗
PubMed1989

[Changed chemosensory identity following experimental bone marrow transplantation: recognition by another species].

A new paradigm was constructed using rats as trained animals in order to examine changes appearing in the scent of mice after a fully allogeneic bone marrow transplantation (BMT). Two rats (CAP), deprived of water 20 hours before each training session, were trained in an olfactometer to discriminate two fully allogeneic mice strains (C3H, C57) via their urine odors. Reinforcement for identification of the St was provided by a drop of water. After discrimination was built-up, the reinforcement schedule was reduced stepwise in defined blocks of trials, in order to allow transfer-of-training tests, to which urine samples of allogeneic reconstituted BMT-chimeras (C57----C3H and C3H----C57) were submitted. It was confirmed that the strain-specific urine odors of the recipients were changed by a fully allogeneic BMT. The results also showed that the urine odors of allogeneic reconstituted chimeras differed from the specific urine odor of the donor strain.

Animals↗
PubMed1989

[Exchange of the hematopoietic system changes chemosensory identity].

It has been shown that the scent of mice changes after a bone marrow transplantation. Previously obtained results were re-examined with a new design that rules out possible avoidance learning effects. Two BALB/c mice, deprived of water for 20 hours each day, were trained in a Y-maze to discriminate two fully allogeneic mice strains (C3H = S+ and C57 = S-) via their urine odor. Reinforcement for correct choice was provided by a drop of water. Urine samples of different fully allogeneic mice strains (C3H, C57 and A/J) and bone marrow transplanted chimeras (C57----C3H and C3H----C57) were submitted to different "transfer of training" -tests. In the conditioning paradigm used, the animals learn to identify S+ and also do not avoid S- after the training. The urine odor of the C57----C3H-chimeras was found to be different from the strain-specific urine odor of C3H animals. Since this change could not be found in syngeneic transplanted chimeras, it is concluded that it is caused by the graft. The experiments failed, however to demonstrate that the urine odor of allogeneic chimeras is constituted solely by donor- and recipient-specific components.

Animals↗
PubMedDate not supplied

Olfactory cues associated with the major histocompatibility complex.

Besides its immunological function of self/non-self discrimination the major histocompatibility complex (MHC) has been recognized as a possible source of individual specific body odors. Dating back to speculations on the role of the extraordinary polymorphism of the MHC as background of an individual chemosensory identity and to early observations of MHC-dependent mate choice in inbred strains of mice, systematic experimental studies revealed a first evidence for H-2 related body odors in this species. Meanwhile a large number of animal studies with rodents and a series of field studies and experiments with humans have extended our knowledge of MHC-related odor signals and substantiated the hypothesis of immunogenetic associated odor types. These results suggest that the most prominent feature of the MHC, its extraordinary genetic diversity, seems in part to be selectively maintained by behavioral mechanisms which operate in contemporary natural populations. The high degree of heterozygosity found in natural populations of most species seems to be promoted by non-disease-based selection such as mating preferences and selective block of pregnancy.

Animals↗
PubMedDate not supplied

The major histocompatibility complex and the chemosensory signalling of individuality in humans.

The chemosensory identity of mice and rats is determined partly by polymorphic genes of the major histocompatibility complex (MHC). In inbred strains of mice, as well as in seminatural populations, MHC-associated mating preferences selectively influence reproductive success, thus serving to promote heterozygocity in the MHC. In order to determine whether MHC-associated chemosignals are present in humans, two studies were conducted. In a first study, olfactory identification of MHC-associated chemosignals was conducted on 12 trained rats' responses to the urine odors of humans. In a second study, MHC-associated olfactory cues in humans were analyzed by means of gas chromatography. The results indicate that the urine odors of humans are associated with the MHC and demonstrate that the profile of volatile components in the urine odors shows some association with the MHC. Furthermore, results show that a profile of some specific components, as well as a few ubiquitous volatiles, constitutes MHC-associated odor signals in humans.

Animals↗
PubMedDate not supplied

Molecular forms of soluble HLA in body fluids: potential determinants of body odor cues.

The major histocompatibility complex (MHC) has been linked to encoding for individual olfactory identity. Experiments in mice and rats proved that behavior and mating were, at least in part, determined by genes within the MHC. This study was aimed at investigating whether sHLA are excreted in human urine, saliva and sweat. In particular examination of the molecular forms in these fluids would give clues to whether break down forms of soluble MHC molecules might participate in shaping behavior. Major bands of 45, 40, and 23 kD were detectable. Increased levels of sHLA were measured using a quantitative ELISA in urine shortly before ovulation decreasing to normal levels thereafter. In animal models strain specific MHC-linked odor cues have been detected in urine. Thus, excretion of sHLA in urine might indicate a similar role for these molecules in humans.

Body Fluids↗