Biomedical subjects

J Fritz

Publications and source records attributed to J Fritz.

At least 19 recordsLinked to original sources

PubMed2001

Perivenous support reduces early changes in human vein grafts: studies in whole blood perfused human vein segments.

BACKGROUND: Patency of vein grafts in coronary artery bypass grafting procedures is generally less favorable than those of selected arterial grafts. However, vein grafts still are needed in cardiac operations. It would be desirable to find measures to improve the patency of vein grafts next to antithrombotic regimens. Animal studies demonstrated that arterial pressure induces overdistention of the thin-walled vein grafts and that prevention of this overdistention with extravascular support ameliorates the arterialization process with, subsequently, more favorable patency. To evaluate whether perivenous stenting of the rather muscular human vein grafts is also beneficial, we designed an in vitro model to study the early effects of perivenous support in human vein grafts. METHODS: Seven paired segments of human vein graft obtained during coronary artery bypass grafting procedures were placed in a perfusion circuit and perfused simultaneously with autologous whole blood, with a pressure of 60 mm Hg (nonpulsatile flow). After 30 minutes of perfusion, one segment, and after 60 minutes of perfusion, the remaining segment were taken for histologic and immunohistochemical examination. In the next experiments 7 segments of human vein graft were placed in the circuit and supported with a polytetrafluoroethylene graft to prevent overdistention with 7 unstented segments as controls. RESULTS: In unsupported vein grafts perfused with autologous blood under a pressure of 60 mm Hg, a complete de-endothelialization was shown after 1 hour of perfusion. In the study vein grafts, with a perivenous polytetrafluoroethylene graft preventing overdistention (n = 7), the endothelium remained intact. Electron microscopic investigation of the media showed severe damage in the circular smooth muscle layer in the unstented group, whereas in the stented group almost no injury was found. CONCLUSION: In our in vitro closed-loop model, reproducible vessel wall changes were observed in all human vein graft specimens studied. The beneficial effect of perivenous support could also be established for the human greater saphenous vein, providing a basis for clinical application.

Blood Pressure↗

PubMed2000

Translating biomolecular recognition into nanomechanics.

We report the specific transduction, via surface stress changes, of DNA hybridization and receptor-ligand binding into a direct nanomechanical response of microfabricated cantilevers. Cantilevers in an array were functionalized with a selection of biomolecules. The differential deflection of the cantilevers was found to provide a true molecular recognition signal despite large nonspecific responses of individual cantilevers. Hybridization of complementary oligonucleotides shows that a single base mismatch between two 12-mer oligonucleotides is clearly detectable. Similar experiments on protein A-immunoglobulin interactions demonstrate the wide-ranging applicability of nanomechanical transduction to detect biomolecular recognition.

Animals↗

PubMed2000

Stimulus enhancement in greylag geese: socially mediated learning of an operant task.

We recently observed the spreading of a novel tradition in a flock of semiferal greylag geese, Anser anser: an increasing number of individuals began to bite and chew the stems of butterbur, Petasites hybridus. Because this behaviour spread particularly fast within families, social learning seemed to be involved. We therefore designed an experiment with hand-reared goslings, which were socially imprinted on humans, to investigate whether and how the observation of an experienced tutor affects the acquisition of a novel skill. Goslings had to open the gliding lid of a box to get at a food reward. To each of seven hand-reared observers a human tutor demonstrated where and how to open the lid, whereas seven controls remained untutored. All observers learned to perform the task but only one of the controls succeeded. The observers explored more often at the position shown by the tutor than elsewhere and seemingly learned by trial and error. In contrast, control birds explored primarily at positions that did not allow them to open the box. These results indicate that in greylag goslings the observation of an experienced model facilitates the learning of an operant task. We conclude that stimulus enhancement followed by operant conditioning were the mechanisms involved, which may have accounted for the fast spread of the stem-chewing tradition between family members. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗

PubMed2000

Supramolecular structure of a new family of circular proteoglycans mediating cell adhesion in sponges.

Aggregationfactors are the molecules responsible for species-specific cell adhesion in sponges. Here, we present the structure of the aggregation factor from the marine sponge Microciona prolifera, which constitutes the first description of a circular proteoglycan. We have analyzed chemically dissociated and enzymatically digested aggregation factor with atomic force microscopy, agarose gel electrophoresis, and Western blots using antibodies against the protein and carbohydrate moieties. Twenty units from each of two N-glycosylated proteins, MAFp3 and MAFp4, form the central ring and radiating arms, respectively, stabilized by a hyaluronidase-sensitive component. MAFp3 carries a 200-kDa glycan involved in homologous self-interactions between aggregation factor molecules, whereas MAFp4 carries a 6-kDa glycan that binds cell surface receptors. A 68-kDa lectin found in cell membranes of several sponge species binds the aggregation factor and its protein-free glycans, as well as chondroitin sulfate and hyaluronan. Here, we show that despite their lack of clear sequence homologies with other known proteoglycan structures, the protein and carbohydrate components of sponge aggregation factors assemble to form a supramolecular complex remarkably similar to classical proteoglycans.

Animals↗

PubMed2000

Vitamin D in schizophrenia, major depression and alcoholism.

25-Hydroxyvitamin D3, 1,25-dihydroxyvitamin D3, calcium, phosphate and parathyreoidal hormone levels were assessed in 34 patients with schizophrenia (DSM-III-R, 44% female, mean age 38.9 +/- 2.1 years), 30 patients with alcohol addiction (16% female, mean age 48.7 +/- 2.2 years), 25 patients with major depression (56% female, mean age 57.6+/- years) and 31 healthy controls. Only 25-hydroxyvitamin D3 and 1,25-dihydroxvitamin D3 levels were significantly lower in all groups of psychiatric patients than in normal controls, but not phosphate, calcium and parathyreoidal hormone levels. Significant differences in the vitamin D levels could not be found between the three psychiatric groups. These findings do not support the idea that vitamin D is specifically involved in the pathophysiology of depression. The difference in patients as compared to the healthy controls might be related to a different social background resulting in differing habits e.g. of nutrition.

Adult↗

PubMed2000

A cantilever array-based artificial nose

We present quantitative and qualitative detection of analyte vapors using a microfabricated silicon cantilever array. To observe transduction of physical and chemical processes into nanomechanical motion of the cantilever, swelling of a polymer layer on the cantilever is monitored during exposure to the analyte. This motion is tracked by a beam-deflection technique using a time multiplexing scheme. The response pattern of eight cantilevers is analyzed via principal component analysis (PCA) and artificial neural network (ANN) techniques, which facilitates the application of the device as an artificial chemical nose. Analytes tested comprise chemical solvents, a homologous series of primary alcohols, and natural flavors. First differential measurements of surface stress change due to protein adsorption on a cantilever array are shown using a liquid cell.

Journal Article↗

PubMed1999

Interaction of the pore-forming protein equinatoxin II with model lipid membranes: A calorimetric and spectroscopic study.

The interactions of equinatoxin II (EqTxII) with zwitterionic (DPPC) and anionic (DPPG) phospholipids and an equimolar mixture of the two phospholipids (DPPC/DPPG) have been investigated by differential scanning calorimetry (DSC), CD-spectropolarimetry, intrinsic emission fluorescence spectroscopy, and ultrasonic velocimetry. EqTxII binds to small unilamellar vesicles formed from negatively charged DPPG lipids, causing a marked reduction in the cooperativity and enthalpy of their gel/liquid-crystalline phase transition. This transition is completely abolished at a lipid-to-protein ratio, L/P, of 10. For the mixed DPPC/DPPG vesicles, a 2-fold greater lipid-to-protein ratio (L/P = 20) is required to abolish the phase transition, which corresponds to the same negative charge (-10) of lipid molecules per EqTxII molecule. The disappearance of the phase transition of the lipids apparently corresponds to the precipitation of the lipid-protein complex, as suggested by our sound velocity measurements. Based on the far-UV CD spectra, EqTxII undergoes two structural transitions in the presence of negatively charged vesicles (DPPG). The first transition coincides with the gel/liquid-crystalline phase transition of the lipids, which suggests that the liquid-crystalline form of negatively charged lipids triggers structural changes in EqTxII. The second transition involves the formation of alpha-helical structure. Based on these observations, we propose that, in addition to electrostatic interactions, hydrophobic interactions play an important role in EqTxII-membrane association.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1999

Variables influencing the origins of diverse abnormal behaviors in a large sample of captive chimpanzees (Pan troglodytes).

The developmental origin of abnormal behaviors is generally associated with early rearing environments that lack sufficient physical and sensory stimulation. However, other factors should also be considered. A large sample of captive chimpanzees (128 males and 140 females) was surveyed for the presence or absence of 18 abnormal behaviors. Origin variables included the subject's source (zoo, pet, performer, or laboratory), rearing (mother- or hand-reared), and sex. Animals were assessed while held at the Primate Foundation of Arizona, University of Texas M. D. Anderson Cancer Center, or White Sands Research Center. There was a confound among origin variables; more hand-reared animals than expected were from laboratories. Logistic regression tested the relationship of rearing and source, with sex as a secondary predictor variable, to each of the abnormal behaviors. There was no clear association between any abnormal behavior and source. However, for coprophagy, relative to animals from the laboratory, zoo animals tended to show a higher prevalence, while performers tended to show a lower prevalence (when rearing and sex were controlled). Rocking and self-sucking were significantly more likely in hand-reared animals. Coprophagy and depilation of self were significantly more likely in mother-reared animals. When rearing and source were statistically controlled, the only significant sex difference was a higher prevalence of coprophagy in females and a higher prevalence of rocking in males. In a second, smaller sample of 25 males and 33 females from Southwest Foundation for Biomedical Research, no significant sex association was found for coprophagy, urophagy, rocking, or self-depilation. In this second sample, coprophagy was also significantly more likely in mother-reared than hand-reared subjects. The association of some abnormal behaviors with mother-rearing suggests that some form of social learning may be involved in the origin of some of these behavior patterns. This indicates that some abnormal behaviors may not be always be indicative of reduced psychological well-being in captive chimpanzees.

Animals↗

PubMed1999

Arthritis of the finger joints: a comprehensive approach comparing conventional radiography, scintigraphy, ultrasound, and contrast-enhanced magnetic resonance imaging.

OBJECTIVE: A prospective study was performed comparing conventional radiography, 3-phase bone scintigraphy, ultrasound, and magnetic resonance imaging (MRI) with precontrast and dynamic postcontrast examinations in 60 patients with various forms of arthritis including rheumatoid arthritis (RA), spondyl-arthropathy, and arthritis associated with connective tissue disease. METHODS: A total of 840 finger joints were examined clinically and by all 4 imaging methods. Experienced investigators blinded to the clinical findings and diagnoses analyzed all methods independently of each other. The patients were divided into 2 groups. Group 1 included 32 patients (448 finger joints) without radiologic signs of destructive arthritis (Larsen grades 0-1) of the evaluated hand and wrist and group 2 included 28 patients (392 finger joints) with radiographs revealing erosions (Larsen grade 2) of the evaluated hand and/or wrist. RESULTS: Clinical evaluation, scintigraphy, MRI, and ultrasound were each more sensitive than conventional radiography in detecting inflammatory soft tissue lesions as well as destructive joint processes in arthritis patients in group 1. All differences were statistically significant. We found ultrasound to be even more sensitive than MRI in the detection of synovitis. MRI detected erosions in 92 finger joints (20%; 26 patients) in group 1 that had not been detected by conventional radiography. CONCLUSION: Our data indicate that MRI and ultrasound are valuable diagnostic methods in patients with arthritis who have normal findings on radiologic evaluation.

Adult↗

PubMed1999

Social learning in common ravens, Corvus corax.

We conducted an experiment to investigate whether the presence of a conspecific model can promote the acquisition of a motor task in common ravens. For this purpose, dyads, either of control birds or of model-observer pairings, were allowed to operate together in an arena with a set of identical boxes. Each box consisted of two compartments each containing a reward of three pieces of meat. The compartments were closed by gliding lids with red flaps on their front, opening horizontally in opposite directions. Naive control individuals opened the lids exclusively by levering, that is, jumping on top of the box, inserting the beak at the posterior rim of the lid and pushing it open. Models were trained to demonstrate an alternative opening technique, pulling at the front flap, then jumping on top of the box to get at the reward. In contrast to the control birds, observers initially opened boxes both ways, by pulling and levering. Furthermore, observers approached the boxes more quickly and showed less fearful behaviour than the control birds, which we attribute to the enhancing effect of the model. We discuss both stimulus enhancement and motor imitation as possible learning mechanisms. Even though observers initially obtained a considerable amount of reward produced by the models, scrounging evidently did not inhibit learning. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗

PubMed1999

[Computer-assisted performance documentation. Effects in orthopedics and trauma surgery on budgets and reimbursement].

Since 1995 German health maintenance laws require hospitals to document and code all referrals, admissions and discharges using the 4-digit ICD. Operative procedures are documented and coded using the ICPM. Beginning in January 1996, reimbursement for health services requires a diagnosis-related billing and payment for special procedures. The decision for billing is based on documented diagnosis and therapy. This extended request for documentation makes an online access to diagnosis and therapy with a computer-assisted coding system advisable. In 1996 in our hospital each diagnosis and operation was manually documented and coded on a form. Since the beginning of 1997, documentation and coding has been exclusively computer-assisted. On the basis of documented diagnosis and therapy the computer provides the route of reimbursement. Retrospectively we evaluated the number of charged diagnosis-related billings and payments for special procedures from January to April of 1996 and 1997. It became evident that with computer-assisted documentation and coding the number of detected and charged diagnosis-related billings and payments for special procedures was significantly increased in comparison with the previous year.

Budgets↗

PubMed1999

Growth factors in distraction osteogenesis. Immuno-histological pattern of TGF-beta1 and IGF-I in human callus induced by distraction osteogenesis.

Although growth factors have been demonstrated during bone healing, their presence has not yet been confirmed in callus distraction. Therefore, in 3 patients we searched for cytokines during callus distraction. Bone biopsies were immuno-histochemically stained for TGF-beta1, IGF-I, TGF-beta type II receptor, IGF receptor, and proliferating cell nuclear antigen (PCNA). Histologically we found immature woven bone in the middle of the callus zone and increasing calcification and lamellar bone in the re-modelling zone. Osteoblasts and fibroblast-like cells in the middle zone, and osteoblasts in all zones stained for TGF-beta and its receptor. The number of positive staining cells related to proliferous activity as assessed both by PCNA, and by bone density in radiographs. IGF-I could be detected everywhere. In conclusion, growth factors are present in bone formation and in areas of re-modelling during callotasis. Their relation to proliferous activity and radiographic density supports their involvement in osteogenesis.

Adult↗

PubMed1999

Dual streams of auditory afferents target multiple domains in the primate prefrontal cortex.

'What' and 'where' visual streams define ventrolateral object and dorsolateral spatial processing domains in the prefrontal cortex of nonhuman primates. We looked for similar streams for auditory-prefrontal connections in rhesus macaques by combining microelectrode recording with anatomical tract-tracing. Injection of multiple tracers into physiologically mapped regions AL, ML and CL of the auditory belt cortex revealed that anterior belt cortex was reciprocally connected with the frontal pole (area 10), rostral principal sulcus (area 46) and ventral prefrontal regions (areas 12 and 45), whereas the caudal belt was mainly connected with the caudal principal sulcus (area 46) and frontal eye fields (area 8a). Thus separate auditory streams originate in caudal and rostral auditory cortex and target spatial and non-spatial domains of the frontal lobe, respectively.

Acoustic Stimulation↗

PubMed1998

Force-mediated kinetics of single P-selectin/ligand complexes observed by atomic force microscopy.

Leukocytes roll along the endothelium of postcapillary venules in response to inflammatory signals. Rolling under the hydrodynamic drag forces of blood flow is mediated by the interaction between selectins and their ligands across the leukocyte and endothelial cell surfaces. Here we present force-spectroscopy experiments on single complexes of P-selectin and P-selectin glycoprotein ligand-1 by atomic force microscopy to determine the intrinsic molecular properties of this dynamic adhesion process. By modeling intermolecular and intramolecular forces as well as the adhesion probability in atomic force microscopy experiments we gain information on rupture forces, elasticity, and kinetics of the P-selectin/P-selectin glycoprotein ligand-1 interaction. The complexes are able to withstand forces up to 165 pN and show a chain-like elasticity with a molecular spring constant of 5.3 pN nm-1 and a persistence length of 0.35 nm. The dissociation constant (off-rate) varies over three orders of magnitude from 0.02 s-1 under zero force up to 15 s-1 under external applied forces. Rupture force and lifetime of the complexes are not constant, but directly depend on the applied force per unit time, which is a product of the intrinsic molecular elasticity and the external pulling velocity. The high strength of binding combined with force-dependent rate constants and high molecular elasticity are tailored to support physiological leukocyte rolling.

Base Sequence↗

PubMed1998

Different behavior of human osteoblast-like cells isolated from normal and heterotopic bone In vitro.

In this study, a characterization of human bone-forming cells responsible for heterotopic ossification was carried out in vitro. The biological and biochemical cell characteristics of the heterotopic osteoblast-like (HOB) cells were compared with those of orthotopic osteoblast-like (OB) cells from normal bone and stromal bone marrow cells believed to contain a subpopulation of osteogenic precursor cells. We found that HOB's from the spongiosa of heterotopic ossification required less time until the beginning of migration and the achievement of confluence in vitro compared with OBs from femoral shaft spongiosa. The fraction of mitotically active cells assessed by a clonogenic assay was higher as well in HOB cells. The in vitro studies of mitogenesis and the efficiency of colony formation of osteogenic cells indicate that with increasing differentiation and relative age they become more dependent on growth factors in the medium, otherwise the morphology of osteoblast-like cells changes and they pass irreversibly into the postmitotic stage of the cell cycle. The activity of the alkaline phosphatase is distinctly higher in the HOB than in the OB cells, HOB cells exhibit a lower level of osteocalcin expression compared with OB cells. No significant difference was found between OB and HOB cells in the amount of procollagen of type I sequestered by the cells. After 30 days, HOB and OB cells formed a mineralized matrix on exposure to 2 mM beta-glycerophosphate. Since HOBs were isolated from heterotopic bone that had developed within 3-6 months after hip surgery, the differences in cellular behavior compared with OBs may be attributed to the relatively young age of HOB cells.

Alkaline Phosphatase↗

PubMed1998

Gynecologic and reproductive services for women with developmental disabilities.

A two-phase study using mail-out questionnaires examined the availability and accessibility of gynecologic and reproductive services for women with developmental disabilities. First, 127 women with developmental disabilities responded to queries about the accessibility and type of available services, the providers of necessary care, and satisfaction with the services. The age range of the women was 18-80 years, with a mean age of 40 years. Of the women queried, 40% indicated that they had not received health education regarding gynecologic and reproductive needs, and 27% indicated that they disliked health education about such matters. In the second phase of the study, agencies that provide services to these women were queried about patterns of the providers, available services, and identified barriers, including financial problems, difficulty in finding a provider, family perceptions, and fear of and distaste for examinations. A surprising finding was that more than one-third of the reporting agencies indicated that questions about the identification and treatment of sexual abuse were not applicable to their agencies. The findings are discussed with an emphasis on identified barriers to care, available services, and the implications for nurse practitioner practice.

Adult↗

PubMed1997

Probing single biomolecules with atomic force microscopy.

During the last years, atomic force microscopy (AFM) has developed from a microscopy tool for solid-state surface science toward a method employed in many scientific disciplines, such as biology, for investigating individual molecules on a nanometer scale. This article describes the current status of the imaging possibilities of AFM on RNA, IgG, and gold-labeled cell adhesion proteoglycans, as well as of measurements of intermolecular binding forces between biomolecules in order to investigate their molecular structure, function, and elasticity.

Animals↗

PubMed1997

Protein/amphipathic polyamine complexes enable highly efficient transfection with minimal toxicity.

Ternary complexes of plasmid DNA, histone H1 protein and amphipathic polyamines (PAPA) were able to mediate the efficient transfection of 3T3. HeLa and COS cells in culture. Using both the beta-galactosidase and luciferase reporter gene systems, the transfection efficiency of PAPA complexes was comparable to that of DOSPA/PE cationic liposomes, considered to be a highly-efficient transfection reagent. Using three different assays of cellular toxicity (propidium iodide, BCECF-AM and Trypan Blue), the PAPA complexes caused minimal cellular toxicity. These results indicate that PAPA complexes are useful transfection reagents for the study of gene expression and function in cultured cells.

3T3 Cells↗