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Biomedical subjects

S Raab

Publications and source records attributed to S Raab.

18 recordsLinked to original sources
PubMed2000

Automation of the use of fluorescent microspheres for the determination of blood flow.

Fluorescent-labeled microspheres (FM) are a new tool for the determination of organ blood flow. However, the FM-method is labor intensive, because of the necessity to recover the microspheres from the tissue samples. The aim of this study was to automate the FM-method. A Zymate-Robotic System (Zymark, Idstein, Germany) was modified to handle a novel filtration device. The robot is surrounded by 12 different stations which are necessary to process the samples. It performs the sequential steps which are needed to recover the microspheres from the samples. The dyes are finally released from the FM with a solvent and their fluorescent intensity is measured online using a spectrophotometer (Perkin Elmer, Uberlingen, Germany). The robotic system is able to recover the FM through digestion and filtration of the tissue samples using the new filter, to dissolve the FM and to release the dyes so that their fluorescent intensities can be measured for the calculation of organ blood flow.

Animals↗
PubMed1999

Influences on skatole formation from tryptophan in the pig colon.

Variable amounts of skatole (3-methyl-indole) are formed by microbes out of tryptophan in the colon of pigs. It is resorbed and accumulated in fat, leading to a fecal odor of the meat. We investigated the mechanisms by which differences in diet composition lead to variations in skatole concentrations in blood plasma and fat. The experiments were based on the hypothesis that tryptophan is derived from mucosa cell debris from the small intestine. It was found, that gut cell mitosis is stimulated by the growth factor IGF-I. This factor increases when energy in the diet is high. In addition, the mitotic rate is elevated when high amounts of purines are available in the diet, allowing a more rapid DNA- and RNA-synthesis. Thus, high energy combined with high purines in the diet lead to a remarkable increase of gut cell mitosis which is accompanied by an increase of apoptosis. These apoptotic cells ultimately provide the substrate for skatole formation. In consequence, a dramatically rise of skatole in blood plasma and fat was measurable.

Animals↗
PubMed1999

[A new experimental model for repetitive osseous blood supply measurement].

The aim of this study was to establish a novel model permitting repetitive analysis of osseous perfusion over a period of 33 days using the fluorescent microsphere technique. After implantation of two port systems into the right and left carotid artery in New Zealand rabbits (n = 3), fluorescent microspheres were injected into the left ventricle, while blood samples for reference probes were taken from the descending aorta. Using seven different fluorescently labeled microspheres, injections were repeatedly performed starting 3 days after implantation (t = 0) at days 1, 3, 5, 12, 19, 26, and 33. Osseous blood flow was semiquantitatively analyzed by counting the number of trapped microspheres within the bone sections performed through the distal femur condyle (n = 8) using a fluorescence microscope. Over the entire observation period of 33 days, intraindividual variance in the number of trapped microspheres was low while there were marked interindividual differences between animals. The mean osseous perfusion in the three animals evaluated so far remained constant over the observation period of 33 days. The present model is the first to allow repetitive analysis of osseous perfusion over an observation period of 33 days. Using this model, the role of regional osseous perfusion can be studied under conditions such as impaired bone healing following radiotherapy- and/or chemotherapy, implantation of biomaterials, and transplantation of bone.

Animals↗
PubMed1999

Changes in serum osmolarity influence the function of outer hair cells.

Fast motility of outer hair cells (OHC) is thought to be based on a hydromechanic principle. In vitro, the function of OHCs can be disturbed by a change in the osmolarity of the culture medium. Whether changes in the serum osmolarity in vivo can also interfere with OHC motility has not been investigated as yet. Serum osmolarity of New Zealand White rabbits (n = 18) was elevated by a continuous infusion of glucose 40%, decreased by an infusion of aqua dest, or kept constant by an infusion of saline. OHC function was monitored using distortion products of otoacoustic emissions (DPOAE). Input output curves were established between 2 and 5 kHz (geometric mean of f2) with primaries of levels between 35 and 55 dB SPL. Cochlear perfusion was measured using a fluorescence microsphere method. Elevation of the serum osmolarity from 306 +/- 17 mosm/l to 365 +/- 23 induced a decrease of DPOAE between 3 and 12 dB SPL. Cochlear blood flow increased from 0.11 +/- 0.09 to 0.15 +/- 0.10 ml/min/g. When decreasing the serum osmolarity from 303 +/- 9 to 281 +/- 8 mosm/l, only slight changes of the DPOAE could be verified. As in the control group, cochlear perfusion was almost unchanged. In the control group, neither serum osmolarity nor DPOAE changed. Comparable to findings in vitro, increasing the serum osmolarity can lead to a disturbance of OHC function. In patients suffering from sudden hearing loss. dehydration due to physical or mental stress is often observed. This new and promising pathophysiological concept needs further clinical evaluation.

Acoustic Stimulation↗
PubMed1999

A new sample-processing unit for the fluorescent microsphere method.

The use of fluorescent-labeled microspheres (FM) for measurement of regional blood flow is an attractive alternative to the use of radioactive-labeled microspheres. In the FM method the FM have to be completely recovered from the tissue samples in a time- and labor-intensive process. For this reason, a considerable loss of FM is possible. The aim of this study was to develop a filtration device that allows the tissue sample to remain in a single container throughout the procedure to make the process easier and to avoid the loss of FM. The core of the sample-processing unit (SPU) is a single-tube filtration device with a polyamide wire mesh. The protocol for processing tissue from different organs (heart, kidney, liver, spleen, intestine, muscle, bone, lung, brain) was modified and thus shortened significantly. Furthermore, the SPU allows direct filtration of the blood reference sample without previous digestion. Different experiments showed that the SPU in combination with the new protocol excludes the loss of 15-micrometers FM. The modifications of the whole procedure render it faster and highly standardized.

Animals↗
PubMed1998

Effects of energy and purines in the diet on proliferation, differentiation, and apoptosis in the small intestine of the pig.

The effects of the energy and purine content in the diet on mucosal cell mitosis, function, and apoptosis in the small intestine of pigs were investigated in two experiments. In experiment I, three groups of five pigs were first fed a commercial diet that contained 9.1 MJ metabolizable energy (ME) per kilogram dry matter (DM) and 16.4% crude protein. It was followed by the experimental diets for 5 days each starting with an energy deficit (5.8 MJ ME/kg DM; 7% crude protein) followed by a high-energy diet with low purine content (14.1 MJ ME/kg DM; 13.6% crude protein; 460 mg purines/kg), or alternatively an isocaloric high-purine diet (2,160 mg purines/kg). During experimental periods, blood samples were drawn daily through catheters for insulin-like growth factor-I (IGF-I) determination. The animals were killed at the end of the corresponding feeding period and gut tissue samples were collected. In tissue samples, IGF-I and parameters for the characterization of mitosis (thymidine kinase [TK], proliferating-cell nuclear antigen [PCNA]) and differentiation (RNA content, alkaline phosphatase, sucrase) were measured. The degree of apoptosis was determined histologically. In experiment II, five pigs were fitted with simple T-cannula at the distal jejunum. They were fed the three experimental diets consecutively for 7 days each and sucrase and alkaline phosphatase were measured in digesta (four samples daily). IGF-I in blood but not in tissue clearly responded to the energy content of the diet with a decrease during the deficit and an increase in the two high-energy groups. However, purines had no additional effect on IGF-I. TK, PCNA, and gut weight showed an energy effect on mitosis, which was paralleled by increased peripheral IGF-I. Purines led to a further increase of mitosis, but IGF-I and gut weight were not increased. The degree of mitosis was correlated with higher activities of sucrase and alkaline phosphatase and also with the number of apoptotic cells. The enzyme activity increased from the deficit to the high-energy group and was further elevated due to purines. The results from experiment II also confirm these effects of energy and purines, because the activities of the enzymes in digesta decreased during energy deficit, but increased due to energy and in addition to purines.

Alkaline Phosphatase↗
PubMed1996

Glucocorticoid receptors in the pig intestinal tract and muscle tissue.

Due to the known differences of protein turnover in skeletal muscle (slow turnover) and intestinal tract (rapid turnover), these tissues were analysed for the free glucocorticoid receptor (GR) concentrations. Cytosol was prepared from different parts of pig intestinal tract and two different muscles (longissimus thoracis: ML; trapezius: MT) under either energy restriction (5.8 MJ ME; 4 kg/d) or sufficient supply (14.0 MJ ME; 4 kg/d) for 4 days before sacrification. Care was taken that all samples were obtained within 15 min post-mortem and that premortem treatment did not elevate circulating cortisol. A Scatchard plot was performed both for muscle and gut tissue and the KD (0.4 +/- 0.04 nM; 0.7 +/- 0.02 nM) as well as Bmax (0.2 +/- 0.01 nM; 1.2 +/- 0.02 nM) pointed to specific binding. GR were generally high in intestinal tract irrespective of the anatomical site, but were significantly (P < or = 0.001) higher under energy restriction compared to adequate feeding (103.2 vs. 76.5 fmol/mg protein). GR was much lower in muscle tissues and tended to be slightly higher in MT (with high proportion of red fibres) compared to ML (white fibres) (12.4 vs. 9.1 fmol/mg protein). GR in muscles was not significantly influenced by energy. The tissue specific differences in GR provide the explanation for the known differences in the protein turnover rate.

Animals↗
PubMed1993

Cytomegalovirus infection and pneumonitis. Impact after isolated lung transplantation. Washington University Lung Transplant Group.

Using aggressive surveillance of blood, bronchoalveolar lavage (BAL) fluid, and lung tissue, we sought to determine the incidence of cytomegalovirus (CMV) pneumonitis in isolated lung transplant recipients and to characterize its impact on pulmonary function, chronic rejection, and survival. Forty-six lung transplant recipients who survived greater than 30 days had prospective documentation of CMV infection in blood and BAL fluid and regular surveillance with transbronchial lung biopsy. CMV infection was documented in 92% of patients who were D-/R+, D+/R+, or D+/R-, and the incidence of histologically confirmed CMV pneumonitis among these patients was 75%. No D-/R- patient experienced CMV infection or disease. D+/R- patients experienced more frequent and severe episodes, and ganciclovir prophylaxis during the first 2 wk was not useful. CMV pneumonitis was accompanied by detectable radiographic changes in less than one third of cases. The detection of CMV in BAL fluid was not predictive of CMV pneumonitis on biopsy, except in D+/R- patients during the first 90 days after transplantation. There was no evidence of an adverse impact because of CMV infection on pulmonary function during the first year after transplantation. A relationship between CMV infection and bronchiolitis obliterans could not be documented; however, D+/R- patients had higher morbidity and a trend toward lower survival. In a multivariate analysis, D+/R- status was an independent predictor of death.

Adult↗
PubMed1990

[Attitude of medical students to alternative healing methods].

In Austria, the interest in alternative healing is obviously increasing, particularly among aspiring physicians. Several separate surveys were carried out by the Institute of Social Medicine in Graz among established physicians, general practitioner trainees and students of the Medical Faculty in order to learn something about their attitudes to alternative therapies. The surveys were directed towards the acceptance or refusal and the utilization of main alternative practices. The attempts show the difficulties in obtaining valid information. Only two satisfied the stringent criteria for the evaluation. This showed that popularity of alternative medicine was pronounced with students. The interest could be explained in part by the insufficiencies in the quality of medical education and by the influence of biased mass media.

Attitude of Health Personnel↗
PubMed1985

Influence of major-histocompatibility-complex-compatible and incompatible Langerhans cells on the survival of H-Y-incompatible skin grafts in rats.

BN male trunk skin grafts, the Langerhans cells (LC) of which have been replaced with major histocompatibility complex (MHC)-incompatible Lewis female cells, survive longer on BN female rats than BN male trunk skin grafts bearing BN female LC. Evidence is presented that the privilege afforded these grafts is a consequence of MHC restriction. Thus, supplanting the native LC population of BN male trunk skin grafts with MHC-compatible Lewis.1N female cells has no affect on their survival on BN female rats. Evidence is also presented that H-Y-incompatible isografts deficient in MHC-compatible LC induce tolerance of H-Y.

Animals↗
PubMed1984

Metal/cement interface strength in cemented stem fixation.

To characterize the strength of the interface between stem-type metal implants and bone cements, a fracture mechanics parameter was used. This parameter, the critical strain energy release rate (Gc), was determined from "push-out" tests of cylindrical specimens. The specimens, formed using molds of bone, were maintained and tested at body temperature. The strength of interfaces formed with cancellous bone surrounding the cement mantle was significantly less than the strength of those formed in apposition to cortical bone. A marked degradation of strength was found with saline immersion for SS316LVM/cement interfaces formed with Zimmer regular, Simplex-P, and Zimmer LVC cements. After 60 days of immersion the interface Gc was only 10-20% of the value for bulk cement. Interfaces formed with thin-film polymethylmethacrylate-precoated metals (SS316LVM, Co-Cr-Mo, and Ti-6A1-4V) yielded "dry" Gc values one order of magnitude greater than those measured with interfaces formed with uncoated metals. Moreover, the strength of precoated SS316LVM/cement interfaces formed with all three brands of cement did not change after saline immersion for 60 days.

Alloys↗
PubMed1984

Randomized trial of cyclophosphamide, doxorubicin, and 5-fluorouracil alone or alternating with a "cycle active" non-cross-resistant combination in women with visceral metastatic breast cancer: a Southeastern Cancer Study Group project.

Patients with visceral patterns of metastatic breast cancer were stratified according to dominant metastatic site and performance status and then randomized to therapy with cyclophosphamide, doxorubicin, and 5-fluorouracil (CAF) or CAF alternating with a "cell-cycle active" regimen including cytosine arabinoside, methotrexate with leucovorin rescue, and oncovin ( CAMELEON ). One hundred eighty-seven patients were randomized; response rate for CAF was 44% and for CAF + CAMELEON , 40%. Durations of disease control and survival were not significantly different. Toxicity of CAF was as anticipated with predominant granulocytopenia, vomiting, and alopecia. Toxicity of CAMELEON was less severe than that of CAF, and CAF toxicity was not worsened by preceding courses of CAMELEON ; however, the CAF- CAMELEON regimen was cumbersome and complex leading to both physician and patient noncompliance. Contrary to the preliminary results of a pilot study, and preliminary reports of the present trial suggesting benefit for the CAF- CAMELEON regimen the present randomized trial does not confirm any significant benefit of CAF- CAMELEON over CAF alone in patients with visceral metastatic breast cancer although this conclusion must be viewed in light of the high inevaluability rate due to patient and physician noncompliance.

Agranulocytosis↗
PubMedDate not supplied

Contribution of linear mechanisms to the specification of local motion by simple cells in areas 17 and 18 of the cat.

A reverse correlation technique, which permits estimation of three-dimensional first-order properties of receptive fields (RFs), was applied to simple cells in areas 17 and 18 of cat. Two classes of simple cells were found. For one class, the spatial and temporal RF characteristics were separable, i.e. they could be synthesized as the product of spatial and temporal weighting functions. RFs in the other class were inseparable, i.e. bright and dark subregions comprising each field were obliquely oriented in space-time. Based on a linear superposition model, these observations led to testable hypotheses: (1) simple cells with separable space-time characteristics should be speed but not direction selective and (2) simple cells with inseparable space-time characteristics should be direction selective and the optimal velocity of moving stimuli should be predictable from the slope of the oriented subregions. These hypotheses were tested by comparing responses to moving bars with those predicted by application of the convolution integral. Linear predictions accounted for waveforms of responses to moving bars in detail. For cells with oriented space-time characteristics, the preferred direction was always predicted correctly and the optimal speed was predicted quite well. Most cells with separable space-time characteristics were not direction selective as predicted. The major discrepancies between measured and predicted behavior were twofold. First, 8/32 cells with separable space-time RFs were direction selective. Second, predicted directional indices were weakly correlated with actual measurements. These conclusions hold for simple cells in both areas 17 and 18. The major difference between simple RFs in these areas is the coarser spatial scale seen in area 18. These results demonstrate a significant linear contribution to the speed and direction selectivity of simple cells in areas 17 and 18. Where additional, nonlinear mechanisms are inferred, they appear to act synergistically with the linear mechanism.

Animals↗