PubMed Health⌕ Search

Biomedical subjects

A Sauter

Publications and source records attributed to A Sauter.

At least 19 recordsLinked to original sources
PubMed2007

[Vacuum-assisted closure of nonhealing wounds in head and neck reconstructive surgery].

Chronic wounds are characterized by slow or nonexistent wound healing. Usually their treatment is expensive. Therefore new concepts in management are of interest in order to reduce treatment time and costs. One option is vacuum sealing. The concept of topical negative pressure is not new, and many chronic nonhealing wounds could be closed successfully with the help of vacuum sealing. Until now, there has been no documented case of vacuum sealing in head and neck reconstructive surgery. Our case shows the effectiveness of a vacuum-assisted device in successful closure of a chronic nonhealing wound in this region.

Aged↗
PubMed2006

[Middle-ear adenoma].

In our case we present a 47-year old female patient, who had a history of one year of right-sided recurrent ear pain without any signs of ear-infections. A computer tomography (CT) imaging was carried out. At the mid-modiolar level, the axial CT-scan showed a small contrast-enhancing density in the middle ear space. She refused further investigation until the ear-pain increased and slight hearing loss was present. Again, six months later a CT-scan was performed, and the hyperdense tissue formation engaged the entire middle ear cleft of the right temporal bone. Typical of MEA, no osteolytic signs were present; the skull-base was intact, the air-cell system of the temporal bone showed no osteolysis or deficiency. In the case presented here, we show a MEA which has filled the middle ear with fluid retention in the mastoid with absent destruction of any structure clinically resulting in ear pain and slight conductive hearing loss. These lesions are contrast-enhancing on CT and on magnetic resonance imaging (MRI) have brain-like signal intensity T2-weighted images. In this case, the lesion was exenterated.

Adenoma↗
PubMed2005

Incoherent modulation instability in instantaneous nonlinear Kerr media.

We demonstrate theoretically and experimentally in an optical fiber system that partially temporally incoherent light exhibits modulational instability during its propagation in an instantaneous response nonlinear medium. We show that the modulation frequency and gain are substantially increased with respect to the corresponding values of coherent modulational instability.

Journal Article↗
PubMed2001

Males of social insects can prevent queens from multiple mating.

During copulation, males of Bombus terrestris fill the queen's sexual tract with a mating plug after transferring their sperm. The sticky secretion is produced by the male's accessory glands and disappears within a couple of days. Experiments now show that the primary function of the plug is to reduce the subsequent mating probability of the queen. The plug is not efficient in preventing sperm migration into the spermatheca. Due to its low energetic value, the plug is also unlikely to serve as a nuptial gift. This type of male interference with female mating propensity has so far not been found in social insects. This finding could, at least tentatively, explain why females of B. terrestris may not be able to take advantage of the demonstrated benefits of multiple mating. Furthermore, such male interference could be a more general phenomenon in social insects, with obvious ramifications for the evolution of polyandry in this group.

Animals↗
PubMed2001

Ischemia-induced neuronal expression of the microglia attracting chemokine Secondary Lymphoid-tissue Chemokine (SLC).

Recently, it has been demonstrated that Secondary Lymphoid-tissue Chemokine (SLC) is constitutively expressed in secondary lymphoid organs and controls the homing of naive T-cells and mature dendritic cells. By screening cDNA isolated from ischemic mouse brain, we found expression of SLC mRNA 6 h up to 4 days after the onset of ischemia. In situ hybridization combined with immunohistochemistry showed neurons expressing SLC mRNA in the ischemic area of the cortex. SLC mRNA expression was also found in cultured neurones after various treatments known to induce neuronal death, but not in cultured glial cells. Stimulation with SLC induced intracellular calcium transients and chemotaxis in cultured microglia. Since mRNA encoding CXCR3, an alternative receptor for SLC, but no CCR7 mRNA was found in microglia, we suggest that the effects of SLC on microglia are mediated by CXCR3. This assumption was corroborated by cross-desensitization experiments using IP-10 as a ligand for CXCR3. The inducible expression of SLC in neurones acting on microglia suggests a new and important role of SLC in the neuroimmune system. We propose that SLC is part of a neurone-microglia signaling system which is related to pathological conditions of the brain like ischemia.

Animals↗
PubMed2001

Dynamic patterns of USPIO enhancement can be observed in macrophages after ischemic brain damage.

Cells of the mononuclear phagocytotic system (MPS) are often found near to or within ischemic tissue and can potentially aggravate cellular damage. Hence, visualization of those cells would allow demarcation of putatively affected from intact tissue. Experimental MRI studies have shown that ultrasmall particles of dextran-coated iron oxide (USPIO) are internalized into cells of the MPS. To test if this cell tagging method may be also applied to cerebral infarction, USPIOs were administered to Fisher rats 5.5 h after permanent occlusion of the middle cerebral artery (pMCAO). During the first 2 days USPIO were preferentially found in patches within the lesion and in surrounding areas. On day 4, USPIOs expanded within the core of the lesion. On day 7 they were found predominantly within the boundary area. Histological analysis showed large populations of macrophages containing iron particles in the infarcted tissue. We conclude, therefore, that it is possible to monitor MPS activity after focal cerebral ischemia using USPIOs.

Animals↗
PubMed2001

MRI analysis of the changes in apparent water diffusion coefficient, T(2) relaxation time, and cerebral blood flow and volume in the temporal evolution of cerebral infarction following permanent middle cerebral artery occlusion in rats.

Detailed knowledge of similarities and differences between animal models and human stroke is decisive for selecting clinically effective drugs based on efficacy data obtained preclinically. Differences in the temporal evolution of stroke pathologies between animal models and man have been reported. In view of the importance of this issue for the development of neuroprotective treatments, the temporal evolution of stroke pathologies in the rat permanent middle cerebral artery occlusion (pMCAO) model has been evaluated with magnetic resonance imaging modalities under experimental conditions matching as close as possible those used in humans. Changes in the ipsilateral and contralateral cortex and striatum of cerebral blood flow (CBF) and volume (CBV), apparent diffusion coefficient (ADC), and spin-spin relaxation time (T(2)), as well as total cortical and striatal infarct volumes, calculated from CBF, ADC, and T(2) maps, were determined starting 1 h up to 216 h post-pMCAO. The temporal evolution of the MRI parameters in this rat model was similar to that observed in humans. In particular, the ADC values were decreased for more than 3 days and returned back to baseline between 4 to 8 days, to increase by day 9 only. Thus the stroke pathology in this rat model develops at a similar pace as in stroke patients arguing against a fundamental difference in the mechanisms involved. The infarct volumes however develop differently in this rat model as they invariably increase over the first 48 h, while in humans the evolution of infarct volume is slower and more heterogeneous.

Animals↗
PubMed2001

The long-distance abscisic acid signal in the droughted plant: the fate of the hormone on its way from root to shoot.

Abscisic acid (ABA) is a potent molecule that certainly modifies stomatal behaviour and plant water loss and probably acts to modify the growth of leaves. The hormone is synthesized both in the leaves and the roots of the plant and in the soil and may move freely from plant to soil and soil to plant. It can also move rapidly through the plant in both the xylem and the phloem and will partition between different compartments in different tissues largely as a function of pH. It is described here how perturbations in soil conditions around the roots and the water status of the air can modify the fluxes of ABA around the plant and its accumulation in different compartments and different tissues. These fluxes can be interpreted as signals of different stresses imposed on the plant and consideration is given to how different perturbations can exert subtle changes which are manifest as modified shoot growth rates and functioning. Most emphasis in the discussion is placed upon the plant's responses to the imposition of soil and atmospheric drought.

Abscisic Acid↗
PubMed2000

Distinct influence of the group III metabotropic glutamate receptor agonist (R,S)-4-phosphonophenylglycine [(R,S)-PPG] on different forms of neuronal damage.

With this study we evaluated the influence of (R, S)-4-phosphonophenylglycine [(R,S)-PPG], a selective group III metabotropic glutamate receptor agonist, on excitotoxic, hypoxic/hypoglycaemic and ischaemic cerebral damage in rodents. Consistent with previous data showing neuroprotective and anticonvulsive effects (Gasparini, F., Bruno, V., Battaglia, G., Lukic, S., Leonhardt, T., Inderbitzin, W., et al., 1999. (R, S)-4-Phosphonophenylglycine, a potent and selective group III metabotropic glutamate receptor agonist, is anticonvulsive and neuroprotective in vivo. Journal of Pharmacology and Experimental Therapeutics 290, 1678-1687), we found pronounced neuroprotective effects with (R,S)-PPG (300 nmol) in a model of excitotoxicity, i.e. quinolinic acid-induced striatal lesions in rats. However, neither in focal cerebral ischaemia in mice nor in global cerebral ischaemia in gerbils or rats did (R,S)-PPG have any significant influence on the extent of neuronal damage. In a model of hypoxia/hypoglycaemia in acutely isolated hippocampal slices, however, (R,S)-PPG led to an improved recovery of population spike amplitude. As acutely isolated hippocampal slices are only viable for a few hours, these electrophysiological recordings can only be performed in a limited time window after the challenge-when most probably excitotoxicity is still the predominant influence in hypoxic pathophysiology. From this we conclude that group III mGluR agonists might be promising drugs against damage mediated mainly by excitotoxicity, but less likely against development of neuronal death due to ischaemia.

Action Potentials↗
PubMed2000

Regional brain activation by bicuculline visualized by functional magnetic resonance imaging. Time-resolved assessment of bicuculline-induced changes in local cerebral blood volume using an intravascular contrast agent.

Functional magnetic resonance imaging (fMRI) has been applied to study rat focal brain activation induced by intravenous administration of the GABA(A) antagonist bicuculline. Using magnetite nanoparticles as a blood pool contrast agent, local changes in cerebral blood volume (CBV) were assessed with high temporal (10 s) and spatial (0.35 x 0.6 mm(2)) resolutions. Upon infusion of the bicuculline region-specific increases in CBV have been observed, suggesting CBV to reflect brain activity. During the first 2 min, the signal increases were predominant in the cortex, followed by increases in other brain areas, such as the caudate putamen, thalamus and cerebellum. Ten minutes after the start of infusion, a dominant response was observed in the thalamus, while in the caudate putamen a biphasic response pattern was seen. The magnitude of the signal responses in all brain regions was dependent on the dose of bicuculline and, in general, matched the known distribution of GABA(A) binding sites. This study suggests that pharmacological fMRI, displaying brain function at the highly specific level of drug-receptor interaction, should foster our understanding of normal and pathological brain function.

Animals↗
PubMed2000

Cytoprotection does not preserve brain functionality in rats during the acute post-stroke phase despite evidence of non-infarction provided by MRI.

In animal models of stroke the promise of a therapy is commonly judged from infarct size measurements, assuming that a reduction in infarct size results in reduction of the functional deficits. We have evaluated the validity of the concept that structural integrity translates into functional integrity during the acute post-stroke period (24 h). Unilateral permanent middle cerebral artery occlusion (pMCAO) in Fischer F344 rats leads to infarcts comprising the ipsilateral striatum and cortical structures, including the somatosensory cortex. Infarct volumes were assessed using magnetic resonance imaging (MRI) methods (T(2), diffusion, perfusion MRI). The functional integrity of the somatosensory cortex was assessed by functional MRI (fMRI) measuring changes in local cerebral blood volume, and by assessing the forelimb grip strength and the beam-walking performance of the animals. Treatment with the calcium antagonist isradipine (2.5 mg/kg injected s.c. immediately after pMCAO) reduced the total infarct size by more than 40% compared to vehicle-injected controls. In particular, the ipsilateral somatosensory cortex appeared normal in diffusion- and T(2)-weighted MRI images. In sham-operated rats simultaneous electrical stimulation of both forepaws led to similar activation of both somatosensory cortices, while in pMCAO animals given vehicle only the contralateral cortex showed an fMRI response. Similarly, in pMCAO rats treated with isradipine, functional activation following bilateral electrical stimulation was only detected in the contralateral somatosensory cortex despite the normal appearance of the ipsilateral cortex in MRI images. Furthermore, fMRI responses to pharmacological stimulation with bicuculline were virtually absent in the ipsilateral somatosensory cortices both in vehicle- and isradipine-treated rats. Finally there was no significant difference between vehicle- and isradipine-treated animals upon the performance of beam-walking test or in forelimb grip strength. It is concluded that during the acute (24 h) post-occlusion period, structural integrity in the somatosensory cortex revealed by MRI does not translate into preservation of function.

Adenosine Triphosphate↗
PubMed2000

Two orcokinins and the novel octapeptide orcomyotropin in the hindgut of the crayfish Orconectes limosus: identified myostimulatory neuropeptides originating together in neurones of the terminal abdominal ganglion.

The tridecapeptides Asn(13)-orcokinin and Val(13)-orcokinin, two known members of the orcokinin neuropeptide family native to crustaceans, and a novel octapeptide, orcomyotropin, FDAFTTGFamide, have been identified from extracts of hindguts of the crayfish Orconectes limosus using an isolated hindgut contractility bioassay, high-performance liquid chromatography, microsequencing and mass spectrometry. All three peptides display strong inotropic actions on crayfish hindguts. Orcomyotropin showed higher potency than the two orcokinins. Threshold concentration was approximately 5 x 10(-12)mol l(-1)versus 10(-10)mol l(-1) for the two orcokinins. An approximately fivefold increase in contraction amplitude was observed with 10(-9)mol l(-1) orcomyotropin and 10(-7)mol l(-1) of the orcokinins. Asn(13)- and Val(13)-orcokinin did not differ significantly with regard to their biological effects. Semi-isolated crayfish hearts and locust oviducts did not respond to the three peptides. Immunocytochemistry using antisera against Asn(13)-orcokinin and orcomyotropin showed that these neuropeptides are co-localized in approximately 80-90 neurones of the terminal abdominal ganglion that have been shown to innervate the entire hindgut muscularis via the intestinal nerve. The neurones form elaborate terminal branches preferentially on longitudinal hindgut muscles. Orcomyotropin is a novel crustacean member of the GF-amide family of myotropic and/or allatotropic neuropeptides from annelids, molluscs and insects.

Amino Acid Sequence↗
PubMed2000

Radial transport of abscisic acid conjugates in maize roots: its implication for long distance stress signals.

Conjugated, alkaline hydrolysable ABA (predominantly abscisic acid glucose ester, ABA-GE), which is transported in the xylem from roots to shoots of Zea mays L. plants, has its origin in the root symplast rather than from soil, although it was detectable in soil solution with concentrations up to 30 nM. External ABA glucose ester cannot be dragged with the water flow across the exodermis and the endodermis because of its hydrophobic properties. Experimental evidence is presented that enzymes in the cortical apoplast cleave ABA-GE thus releasing ABA from its conjugates. Liberated ABA can then be translocated apoplastically and symplastically to the xylem vessels. Endogenous ABA-GE can be released from isolated cortical and stelar tissues to the surrounding media, with rates that are up to 5-fold higher from stelar tissues than those from cortical tissues. Release of ABA-GE is highest under conditions of inhibited ABA-metabolism.

Abscisic Acid↗
PubMed2000

Extracellular beta-glucosidase activity in barley involved in the hydrolysis of ABA glucose conjugate in leaves.

Abscisic acid conjugate concentrations increased in barley xylem sap under salinity, whereas it remained at a low level in the intercellular washing fluid (IWF) of barley primary leaves (Hordeum vulgare cv. Gerbel). Here it is shown that IWF contains beta-glucosidase activity which releases abscisic acid (ABA) from the physiologically inactive ABA-glucose conjugate pool in the leaf apoplast. The following data support this conclusion and give the first biochemical and physiological characterization of the extracellular glucosidase activity in barley. Free ABA was released by the incubation of ABA glucose ester with IWF. The product exhibited the retention time of authentic ABA upon separation by thin layer chromatography and was identified by ABA-ELISA. p-Nitrophenol-beta-D-glucopyranoside (pNPG) was used as the substrate for beta-glucosidases. The K(M)(pNPG) was 1.8 mmol l(-1). The activity was affected by ABA glucopyranoside in a competitive type of inhibition with a K(I) of 400 micromol l(-1). Various hormone conjugates were compared with respect to their inhibitory effect on beta-glucosidase activity. Inhibition was highest for the ABA glucopyranoside and the zeatin riboside, but insignificant for ABA methyl ester and zeatin-9-beta-D-glucoside. The specific activity of the beta-glucosidase was 16-fold greater in IWF as compared to crude leaf extracts confirming its extracellular compartmentation. The activity of beta-glucosidase was strongly increased after growth in hydroponic medium supplemented with NaCl. The data support the hypothesis that the glucose conjugate is a long-distance transport form of ABA.

Abscisic Acid↗
PubMed1999

In vivo magnetic resonance methods in pharmaceutical research: current status and perspectives.

In the last decade, in vivo MR methods have become established tools in the drug discovery and development process. In this review, several successful and potential applications of MRI and MRS in stroke, rheumatoid and osteo-arthritis, oncology and cardiovascular disorders are dealt with in detail. The versatility of the MR approach, allowing the study of various pathophysiological aspects in these disorders, is emphasized. New indication areas, for the characterization of which MR methods have hardly been used up to now, such as respiratory, gastro-intestinal and skin diseases, are outlined in a subsequent section. A strength of MRI, being a non-invasive imaging modality, is the ability to provide functional, i.e. physiological, readouts. Functional MRI examples discussed are the analysis of heart wall motion, perfusion MRI, tracer uptake and clearance studies, and neuronal activation studies. Functional information may also be derived from experiments using target-specific contrast agents, which will become important tools in future MRI applications. Finally the role of MRI and MRS for characterization of transgenic and knock-out animals, which have become a key technology in modern pharmaceutical research, is discussed. The advantages of MRI and MRS are versatility, allowing a comprehensive characterization of a diseased state and of the drug intervention, and non-invasiveness, which is of relevance from a statistical, economical and animal welfare point of view. Successful applications in drug discovery exploit one or several of these aspects. In addition, the link between preclinical and clinical studies makes in vivo MR methods highly attractive methods for pharmaceutical research.

Animals↗
PubMed1999

Magnetic resonance angiography of the rat cerebrovascular system without the use of contrast agents.

We describe and discuss the application of three-dimensional (3D) time-of-flight (TOF) magnetic resonance angiography (MRA) to visualize non-invasively the cerebral vasculature of the rat. MR angiograms of healthy spontaneously hypertensive rats were obtained without the use of contrast agents. Total imaging time ranged from 1 to 50 min for a 3D data set. The influences of the data matrix and the inflow delay on the image quality and the total imaging time are assessed and discussed. Varying the inflow delay yielded in addition semiquantitative information on hemodynamics. The method was applied to obtain angiograms in rat models of permanent and temporal middle cerebral artery occlusion. Occlusion and reopening of the vessel could easily be verified by MRA. However, after reperfusion a slight reduction in blood flow was observed.

Animals↗