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Biomedical subjects

I Fischer

Publications and source records attributed to I Fischer.

At least 19 recordsLinked to original sources
PubMed2006

Effects of two diets on the haematology, plasma chemistry and intestinal flora of budgerigars (Melopsittacus undulatus).

Two groups of 22 budgerigars (Melopsittacus undulatus) were housed for 12 months under identical conditions. One group was fed a commercial seed mixture plus carrots and a mineral supplement, and the other group was fed a commercially formulated diet plus carrots. Samples of blood and faeces were collected initially and after three, six, nine and 12 months. There were no significant differences between the haematological values of the two groups. The group fed the seed mixture had significantly higher concentrations of glucose, albumin, triglycerides and uric acid, and higher activity of aspartate aminotransferase, but the values were within the published reference ranges for normal birds. There were no significant differences between the faecal samples from the two groups, except that the fungus Macrorhabdus ornithogaster was identified in 48.3 per cent of the samples from the group fed the commercially formulated diet but from only 3.4 per cent of the samples from the group fed the seed mixture.

Animal Feed↗
PubMed2006

Long-term fate of neural precursor cells following transplantation into developing and adult CNS.

Successful strategies for transplantation of neural precursor cells for replacement of lost or dysfunctional CNS cells require long-term survival of grafted cells and integration with the host system, potentially for the life of the recipient. It is also important to demonstrate that transplants do not result in adverse outcomes. Few studies have examined the long-term properties of transplanted neural precursor cells in the CNS, particularly in non-neurogenic regions of the adult. The aim of the present study was to extensively characterize the fate of defined populations of neural precursor cells following transplantation into the developing and adult CNS (brain and spinal cord) for up to 15 months, including integration of graft-derived neurons with the host. Specifically, we employed neuronal-restricted precursors and glial-restricted precursors, which represent neural precursor cells with lineage restrictions for neuronal and glial fate, respectively. Transplanted cells were prepared from embryonic day-13.5 fetal spinal cord of transgenic donor rats that express the marker gene human placental alkaline phosphatase to achieve stable and reliable graft tracking. We found that in both developing and adult CNS grafted cells showed long-term survival, morphological maturation, extensive distribution and differentiation into all mature CNS cell types (neurons, astrocytes and oligodendrocytes). Graft-derived neurons also formed synapses, as identified by electron microscopy, suggesting that transplanted neural precursor cells integrated with adult CNS. Furthermore, grafts did not result in any apparent deleterious outcomes. We did not detect tumor formation, cells did not localize to unwanted locations and no pronounced immune response was present at the graft sites. The long-term stability of neuronal-restricted precursors and glial-restricted precursors and the lack of adverse effects suggest that transplantation of lineage-restricted neural precursor cells can serve as an effective and safe replacement therapy for CNS injury and degeneration.

Age Factors↗
PubMed2006

MR imaging of lineage-restricted neural precursors following transplantation into the adult spinal cord.

Neural precursor cell (NPC) transplantation is a promising strategy for treatment of CNS injuries and neurodegenerative disorders because of potential for cell replacement. An important element of future clinical applications is development of a non-invasive procedure to follow NPC fate. We show that neuronal-restricted precursors (NRPs) and glial-restricted precursors (GRPs), NPCs with lineage restrictions for neurons and glia, respectively, can be labeled in vitro with the superparamagnetic iron oxide contrast agent Feridex. Following engraftment into intact adult spinal cord, labeled cells robustly survived in white and gray matter and migrated selectively along white matter tracts up to 5 mm. Localization of cells was reliably established using ex vivo magnetic resonance imaging of spinal cords. Imaging coincided with histological detection of iron and the human alkaline phosphatase transgene in most grafting sites, including the stream of migrating cells. Following transplantation, magnetically labeled cells exhibited mature morphologies and differentiated into neurons, astrocytes, and oligodendrocytes, similar to grafts of unlabeled NRPs and GRPs. Interestingly, Feridex-labeled cells, but not unlabeled cells, induced influx of ED1-positive macrophages/microglia. Small numbers of these phagocytic cells took up iron from grafted cells, while the majority of Feridex label was found in transplanted cells. We conclude that Feridex labeling does not inhibit NPC differentiation and can be used to reliably localize NPCs by MRI following engraftment into adult CNS, with the possible exception of areas of rapidly proliferating cells. The present results are relevant for MR-guided clinical application of transplantation strategies in treatment of spinal cord injury and other CNS pathologies.

Alkaline Phosphatase↗
PubMed2006

Long-term fate of neural precursor cells following transplantation into developing and adult CNS.

Successful strategies for transplantation of neural precursor cells for replacement of lost or dysfunctional CNS cells require long-term survival of grafted cells and integration with the host system, potentially for the life of the recipient. It is also important to demonstrate that transplants do not result in adverse outcomes. Few studies have examined the long-term properties of transplanted neural precursor cells in the CNS, particularly in non-neurogenic regions of the adult. The aim of the present study was to extensively characterize the fate of defined populations of neural precursor cells following transplantation into the developing and adult CNS (brain and spinal cord) for up to 15 months, including integration of graft-derived neurons with the host. Specifically, we employed neuronal-restricted precursors and glial-restricted precursors, which represent neural precursor cells with lineage restrictions for neuronal and glial fate, respectively. Transplanted cells were prepared from embryonic day-13.5 fetal spinal cord of transgenic donor rats that express the marker gene human placental alkaline phosphatase to achieve stable and reliable graft tracking. We found that in both developing and adult CNS grafted cells showed long-term survival, morphological maturation, extensive distribution and differentiation into all mature CNS cell types (neurons, astrocytes and oligodendrocytes). Graft-derived neurons also formed synapses, as identified by electron microscopy, suggesting that transplanted neural precursor cells integrated with adult CNS. Furthermore, grafts did not result in any apparent deleterious outcomes. We did not detect tumor formation, cells did not localize to unwanted locations and no pronounced immune response was present at the graft sites. The long-term stability of neuronal-restricted precursors and glial-restricted precursors and the lack of adverse effects suggest that transplantation of lineage-restricted neural precursor cells can serve as an effective and safe replacement therapy for CNS injury and degeneration.

Age Factors↗
PubMed2006

Unilateral evisceration of an eye following cornea and lens perforation in a sulfur-crested cockatoo (Cacatua galerita).

A 24-year old male sulfur-crested Cockatoo (Cacatua galerita) was presented with a subacute perforation of the cornea without involvement of the lens. The bird was treated conservatively and the eye remained quiescent up to a second traumatic corneal perforation associated with a lens capsule rupture 15 months later. Due to the second perforating trauma of an already blind eye involving the lens, evisceration of the eye was performed. Two months after surgery the cosmetic result was excellent. Treatment options for perforating ocular traumas in captive birds are discussed in detail.

Animals↗
PubMed2006

Chronic regurgitation in a cockatiel (Nymphicus hollandicus) with a trichobezoar.

Crop disorders are very common in small psittacine birds. Psittacine birds are very curious and like chewing on different materials. Therefore, they are predisposed to ingest foreign material. In the literature only very few cases have been reported. This case report describes the clinical examination, the diagnostic workup and the ingluviotomy in a cockatiel with a bezoar in the crop.

Animals↗
PubMed2006

The reliability of isokinetic and isometric leg strength measures among individuals with symptoms of mild osteoarthritis.

AIM: The aim of the study is to evaluate the test-retest reliability of measures of isokinetic and isometric leg strength and joint function among individuals exhibiting symptoms of mild osteoarthritis. Reliable procedures are needed to assess the effectiveness of an intervention on osteoarthritic symptoms. METHODS: Test-retest reliability of two leg strength protocols was assessed using the intraclass correlation coefficient (R). Testing was completed on two occasions separated by 7 days. Eighteen subjects (9 male and 9 female; 54.1+/-11 years) completed an isokinetic testing trial, which consisted of a set of 5 maximal repetitions of the quadriceps and hamstrings at 60 deg/s followed by a set of 15 maximal contractions at 180 deg/s with a 2-min rest between sets and an isometric testing trial, which consist of 3 maximal contractions of the quadriceps for 6 s with a 30-s rest between contractions at 30, 45, and 80 degrees of knee flexion for a total of 9 isometric contractions. A 90-s rest occurred between angles. RESULTS: Most of the isokinetic variables showed moderate to high intraclass reliability (ICC). Two of the calculated isokinetic variables (work fatigue at 180 degrees /s for extension and for flexion) showed low intraclass reliability (ICC=0.78, resp. ICC=0.6). All calculated ICC values of the isometric variables were moderate to high. CONCLUSIONS: Test-retest reliability of isokinetic and isometric leg strength was high, allowing the intervention protocol to monitor changes in leg strength and joint function among those exhibiting symptoms of mild osteoarthritis.

Biomechanical Phenomena↗
PubMed2005

Synchronization of delay-coupled oscillators: a study of semiconductor lasers.

Two delay-coupled semiconductor lasers are studied in the regime where the coupling delay is comparable to the time scales of the internal laser oscillations. Detuning the optical frequency between the two lasers, novel delay-induced scenarios leading from optical frequency locking to successive states of periodic intensity pulsations are observed. We demonstrate and analyze these dynamical phenomena experimentally using two distinct laser configurations. A theoretical treatment reveals the universal character of our findings for delay-coupled systems.

Journal Article↗
PubMed2005

Lineage-restricted neural precursors survive, migrate, and differentiate following transplantation into the injured adult spinal cord.

Fetal spinal cord from embryonic day 14 (E14/FSC) has been used for numerous transplantation studies of injured spinal cord. E14/FSC consists primarily of neuronal (NRP)- and glial (GRP)-restricted precursors. Therefore, we reasoned that comparing the fate of E14/FSC with defined populations of lineage-restricted precursors will test the in vivo properties of these precursors in CNS and allow us to define the sequence of events following their grafting into the injured spinal cord. Using tissue derived from transgenic rats expressing the alkaline phosphatase (AP) marker, we found that E14/FSC exhibited early cell loss at 4 days following acute transplantation into a partial hemisection injury, but the surviving cells expanded to fill the entire injury cavity by 3 weeks. E14/FSC grafts integrated into host tissue, differentiated into neurons, astrocytes, and oligodendrocytes, and demonstrated variability in process extension and migration out of the transplant site. Under similar grafting conditions, defined NRP/GRP cells showed excellent survival, consistent migration out of the injury site and robust differentiation into mature CNS phenotypes, including many neurons. Few immature cells remained at 3 weeks in either grafts. These results suggest that by combining neuronal and glial restricted precursors, it is possible to generate a microenvironmental niche where emerging glial cells, derived from GRPs, support survival and neuronal differentiation of NRPs within the non-neurogenic and non-permissive injured adult spinal cord, even when grafted into acute injury. Furthermore, the NRP/GRP grafts have practical advantages over fetal transplants, making them attractive candidates for neural cell replacement.

Alkaline Phosphatase↗
PubMed2005

Combined effects of neurotrophin secreting transplants, exercise, and serotonergic drug challenge improve function in spinal rats.

OBJECTIVES: To determine the effects of neurotrophin-secreting transplants combined with exercise and serotonergic drug challenges on recovery of hindlimb function in rats with midthoracic spinal cord transection injuries. METHODS: Spinalized animals received transplants of fibroblasts genetically modified to express brain-derived neurotrophic factor and neurotrophin-3 and daily cycling exercise. Hindlimb movement in an open-field test (BBB) was scored weekly. Serotonin agonists were used monthly to further stimulate motor function. Axonal growth was quantified in the transplant and at L5 using immunocytochemical markers. Weights of hindlimb muscles were used to assess muscle atrophy. RESULTS: Neurotrophin-secreting transplants stimulated axonal growth, and cycling prevented muscle atrophy, but individual treatments did not improve motor scores. Combined treatments resulted in improvements in motor function. Serotonergic agonists further improved function in all groups, and transplant groups with exercise achieved weight-supporting levels following drug treatment. CONCLUSION: Combined treatments, but not individual treatments, improved hindlimb function.

Animals↗
PubMed2004

Antibiotic resistance rates and phenotypes among isolates of Enterobacteriaceae in French extra-hospital practice.

Antibiotic resistance among members of the family Enterobacteriaceae was prospectively surveyed by eight French private laboratories over a 5-month period in 1999. A total of 2,599 consecutive and nonduplicate strains were collected, mainly (60.9%) from patients in the community. Most strains (82.9%) derived from urine. Escherichia coli was the predominant (73.9%) organism isolated. The overall rates of antibiotic resistance were as follows: amoxicillin, 53.4%; amoxicillin-clavulanic acid, 27.3%; ticarcillin, 44.2%; piperacillin-tazobactam, 3.2%; cephalothin, 29.2%; cefuroxime, 14.7%; cefoxitin, 11.5%; ceftazidime, 3.6%; cefotaxime, 2.8%; cefepime, 0.3%; imipenem, 0.1%; gentamicin (G), 3.8%; tobramycin (T), 5.0%; netilmicin (Nt), 3.7%; amikacin (A), 0.7%; nalidixic acid, 14.3%; ofloxacin, 10.4%; cotrimoxazole, 21.1%; nitrofurantoin, 12.7%; fosfomycin, 5.2%; tetracycline, 50.1%; and colistin, 12.5%. Beta-lactam resistance phenotypes essentially comprised penicillinase production (33.9%), overexpression of chromosomal cephalosporinase (4.6%), and synthesis of inhibitor-resistant TEM/OXA enzymes (1.5%) or extended-spectrum beta-lactamases (1.5%). Aminoglycoside resistance phenotypes consisted of GTNt (93 strains), TNtA (68 strains), GTNtA (14 strains), T (4 strains), GT (3 strains), G (1 strain), and reduced uptake/permeability (3 strains). Most of the nalidixic acid-resistant strains were resistant to ofloxacin (72.8%). Antibiotic resistance rates and phenotypes varied widely according to the bacterial group and the source of the strains. Significantly higher rates were observed in private healthcare centers than in the community, due to a higher proportion of both resistant species and resistant strains. However, multidrug-resistant isolates, including five extended-spectrum beta-lactamase-producing strains, were also recovered from the community.

Ambulatory Care↗
PubMed2004

ParSeq: searching motifs with structural and biochemical properties.

SUMMARY: Searches for variable motifs such as protein-binding sites or promoter regions are more complex than the search for casual motifs. For example, in amino acid sequences comparing motifs alone mostly proves to be insufficient to detect regions that represent proteins with a special function, because the function depends on biochemical properties of individual amino acids (such as polarity or hydrophobicity). Pure string matching programs are not able to find these motifs; hence, we developed ParSeq, a program that combines the search for motifs with certain structural properties, the verification of biochemical properties, an approximate search mechanism and a stepwise creation of the motif description by allowing to search on previously obtained results. AVAILABILITY: http://www-pr.informatik.uni-tuebingen.de/parseq

Algorithms↗
PubMed2004

High-pressure freezing of epithelial cells on sapphire coverslips.

Rapid freezing of cell monolayers at ambient pressure is limited regarding the thickness of ice crystal damage-free freezing. The specific freezing conditions of the cells under investigation are decisive for the success of such methods. Improved reproducibility of results could be expected by cryoimmobilization at high pressure because this achieves a greater thickness of adequate freezing. In a novel approach, we tested the suitability of sapphire discs as cell substrata for high-pressure freezing. Frozen samples on sapphire were subjected to freeze-substitution while in the same flat sample holders as used for high-pressure freezing. We obtained cells that displayed an excellent preservation of fine structure. Because sapphire is a tissue culture substratum suitable for light microscopy, its use in combination with high-pressure freezing could become a powerful tool in correlative studies of cell dynamics at light and electron microscopic levels.

Aluminum Oxide↗
PubMed2003

Delay dynamics of semiconductor lasers with short external cavities: bifurcation scenarios and mechanisms.

We present a comprehensive study of the emission dynamics of semiconductor lasers induced by delayed optical feedback from a short external cavity. Our analysis includes experiments, numerical modeling, and bifurcation analysis by means of computing unstable manifolds. This provides a unique overview and a detailed insight into the dynamics of this technologically important system and into the mechanisms leading to delayed feedback instabilities. By varying the external cavity phase, we find a cyclic scenario leading from stable intensity emission via periodic behavior to regular and irregular pulse packages, and finally back to stable emission. We reveal the underlying interplay of localized dynamics and global bifurcations.

Journal Article↗