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Biomedical subjects

D Albrecht

Publications and source records attributed to D Albrecht.

At least 37 records · Page 2Linked to original sources
PubMed2000

Identification of angiotensin IV binding sites in the mouse brain by a fluorescent binding study.

In the brain the renin-angiotensin system has been implicated in the regulation of the cardiovascular system as well as of regulation of reproductive hormones, water balance and behavior. Angiotensin II (Ang II) binds to two distinct receptors called AT1 and AT2. Recently a binding site has been discovered which selectively binds a fragment of Ang II. This biologically active Ang II 3-8 fragment is referred to as angiotensin IV (Ang IV) and has been reported to participate in memory acquisition and recall as well as in the regulation of blood flow, neurite outgrowth, angiogenesis and kidney function. The distribution of binding sites for Ang IV within the mouse brain is unknown. Using a nonradioactive binding assay with a fluorescence-coupled Ang IV, we were able to demonstrate specific Ang IV binding sites in the forebrain of mice, in particular in the cortex, the hippocampus, the amygdala, the thalamus and the hypothalamus.

Angiotensin II↗
PubMed1999

Distribution of angiotensin II binding sites in the mouse thalamus: receptor-binding study with fluorescent coupled peptides and their conversion to a light stable product.

Fluorescence-coupled peptides allow a non-radioactive receptor binding study whereby single cells can be examined under a fluorescence microscope. By the combination of such a method with immunohistochemistry, using an HRP-coupled anti-fluorescein antibody, a permanent labeling can be achieved. By using this method the distribution of angiotensin II binding sites has been examined in the mouse thalamus. The results show that a moderate staining was obvious within the thalamus and that the distribution of binding sites in the thalamus is very homogeneous in the mouse brain. In detail, angiotensin II binding sites were found in the anterodorsal nucleus, in the laterodorsal and posterior nucleus of the thalamus, as well as in the lateral geniculate nucleus, the reticular thalamic nucleus and in the zona incerta.

Angiotensin II↗
PubMed1999

Laser-induced thermotherapy combined with hepatic arterial embolization in the treatment of liver tumors in a rat tumor model.

OBJECTIVE: To assess the effect of combined laser-induced thermotherapy (LITT) and hepatic arterial embolization with degradable starch microspheres (DSM) on tumor response and intrahepatic temperature distribution in rats with liver tumors. SUMMARY BACKGROUND DATA: Laser-induced thermotherapy is a promising in situ ablation technique for malignant liver tumors. However, clinical use is still limited, mainly because of the small size of the inducible coagulation necroses. This results in insufficient tumor destruction. METHODS: Colon carcinoma CC531 was implanted in 60 WAG rat livers. Fourteen days later, a silicon catheter was implanted in the hepatic artery for DSM administration. Tumors were exposed to 1064 nm Nd:YAG laser light at 2 watts for 10 minutes from a diffuser tip applicator placed in the tumor. The animals were randomized into a sham-operated control (group I) and three test groups. Group II received DSM alone, group III received LITT alone, and group IV received DSM + LITT. Tumor control was examined 1, 7, and 14 days after treatment. RESULTS: A complete tumor remission was achieved in all rats treated with LITT + DSM (group IV). In contrast, tumor progression was seen in animals treated with LITT alone (group III) or DSM alone (group II), as well as in the sham-operated controls (group I). CONCLUSIONS: The authors' results suggest that the combination of LITT and DSM considerably increases the efficacy of LITT in the treatment of liver metastases in the rat.

Animals↗
PubMed1999

First workshop for detection of heparin-induced antibodies: validation of the heparin-induced platelet-activation test (HIPA) in comparison with a PF4/heparin ELISA.

BACKGROUND: No data exist regarding the inter-laboratory reproducibility of the heparin-induced-platelet-activation (HIPA) test, the most widely used functional assay in Germany for the detection of heparin-induced thrombocytopenia (HIT) antibodies. METHODS: Nine laboratories used an identical protocol to test eight different sera with the HIPA test. Five laboratories also tested the sera with a platelet factor 4 (PF4)/heparin-complex ELISA. Cross-reactivity with danaparoid-sodium was assessed using 0.2 aFXa units instead of heparin in the HIPA test. RESULTS: Two of nine laboratories had no discrepant HIPA test results. Four laboratories differed in one sample, one reported two discrepant results, and two laboratories reported more than two discrepant results. Cross-reactivity with danaparoid-sodium test results differed among laboratories. PF4/heparin ELISA results were identical in all five laboratories. CONCLUSION: The HIPA test requires strict quality control measures. Using both a sensitive functional assay (HIPA test) and a PF4/heparin ELISA will allow detection of antibodies directed to antigens other than PF4/heparin complexes as well as detection of IgM and IgA antibodies with PF4/heparin specificity.

Antibodies↗
PubMed1998

Mapping of angiotensin AT1 receptors in the rat limbic system.

The AT1 receptor is one of the two receptor subtypes able to bind angiotensin II. In the present study, immunohistochemical examination of the distribution of the AT1 receptor in several limbic structures of female rats has been done, revealing new aspects of the distribution of AT1-positive cells. The presence of AT1 receptor expressing cells in the hippocampus and the amygdala is described, but their distribution in these regions has not been examined in a detailed way. We found some notable differences in the distribution of these cells: in female rats, we detected high amounts of labeled cells in the hippocampus, the entorhinal cortex and piriform cortex. In somewhat lower amounts, stained cells could be found in several nuclei of the amygdala (in the basomedial, basolateral, lateral, central and medial nucleus of the amygdala, in the amygdalopiriform transition area and in the amygdalohippocampal transition area as well as in the bed nucleus of the stria terminalis).

Amygdala↗
PubMed1998

Opposite effects of angiotensin II and IV in the lateral nucleus of the amygdala.

In this study the effects of angiotensin II and norleucine1-angiotensin IV have been studied in a horizontal in vitro slice preparation of female rat brains. Extracellular field potentials of the lateral nucleus of the basolateral amygdala were recorded. The results show that angiotensin II significantly increased the amplitude of field potentials induced by the electrical stimulation of the lateral nucleus, whereas norleucine1-angiotensin IV caused a significant decrease in the amplitude of field potentials. The angiotensin-induced effects could be blocked by specific angiotensin receptor antagonists. These opposite effects of angiotensin II and IV on electrophysiological parameters are in agreement with behavioral studies that have demonstrated that angiotensin II and IV produce opposite effects on the retention of an inhibitory shock-avoidance response and correlate with their different effects on the blood vessels.

Amygdala↗
PubMed1998

Tracing of axonal connectivities in a combined slice preparation of rat brains--a study by rhodamine-dextran-amine-application in the lateral nucleus of the amygdala.

In preparation for electrophysiological studies, the fiber pathways within the amygdala of rats have been examined using a combined Nissl- and silver-staining method (Bielshowsky) in horizontal sections of the amygdala. To determine if fibers in the lateral nucleus of the amygdala are in functional connection with other brain regions, an anterograde and retrograde axonal tracing method (application of rhodamine-dextran-amine) was performed. Horizontal slices containing some nuclei of the amygdala (lateral nucleus, basolateral nucleus, central nucleus, medial nucleus), as well as the entorhinal cortex, the hippocampus and parts of the piriform cortex were used. Crystals of rhodamine-dextran-amine were placed in the lateral nucleus. Intra-amygdaloid connections as well as connections to other brain regions were preserved in this preparation. The connectivities of the lateral nucleus with other nuclei of the amygdala (basolateral, medial, central) correspond with the findings made by tracer applications in-vivo. The use of a tracer that is transported in both the antero- and retrograde direction shows the whole spectrum of efferent and afferent fibers which are involved in the projection pattern of the lateral nucleus. To test the usefulness of this preparation for electrophysiological studies, extracellular field potentials were recorded.

Amygdala↗
PubMed1998

Interstitial laser coagulation: evaluation of the effect of normal liver blood perfusion and the application mode on lesion size.

BACKGROUND AND OBJECTIVE: The effect of temporarily interrupted hepatic blood flow and multiple-fiber application on necrosis volume in interstitial laser coagulation (ILC) was investigated. STUDY DESIGN/MATERIALS AND METHODS: Single- and multiple-fiber ILC were performed in porcine livers with normal as well as interrupted perfusion. Temperatures were determined. Lesions were measured and studied by light microscopy 4 hours post-treatment. RESULTS: ILC with multiple-fiber application led to significantly greater individual lesion volumes (3.7 +/- 0.5 cm3) than single-fiber application (2.5 +/- 0.5 cm3) (P < .01). The interruption of hepatic perfusion led to a significant increase in lesion volume with single- (7.5 +/- 1.0 cm3) as well as multiple-fiber application (12.6 +/- 2.2 cm3) (P < .01). Superposition of the lesions in the multiple-fiber application mode was only determined with interrupted perfusion (total volume: 50.3 +/- 6.6 cm3). CONCLUSION: Interruption of hepatic perfusion increases lesion volumes significantly. ILC for treating liver tumors should preferably be performed by application routes that permit temporary interruption of hepatic perfusion.

Animals↗
PubMed1998

Optical properties of native and coagulated human liver tissue and liver metastases in the near infrared range.

BACKGROUND AND OBJECTIVE: Knowledge about optical parameters and the resultant light distribution in laser-treated tissue is important for predicting the effects of laser-induced thermotherapy of liver metastases (LITT). MATERIALS AND METHODS: The absorption and scattering coefficients as well as the anisotropy factors and the optical penetration depths of human liver tissue and colorectal liver metastases were determined at 850, 980, and 1,064 nm under native and thermocoagulated conditions. RESULTS: Liver metastases had a lower anisotropy factor, absorption, and scattering coefficient than healthy liver (P < 0.01), resulting in a significantly higher optical penetration depth in metastatic tissue. Coagulation significantly changes the optical parameters by reducing the optical penetration depth in both tissue types (P < 0.01). CONCLUSIONS: A greater optical penetration depth in metastatic tissue is advantageous for LITT, since larger tumor volumes can be coagulated. At the same time, an adjustment of the application parameters during LITT is necessary to achieve optimal therapeutic success.

Adenocarcinoma↗
PubMed1998

[Laser-induced thermotherapy. Technical prerequisites for treatment of malignant liver tumors].

Laser-induced thermotherapy is an in situ ablation method for the local treatment of liver tumors. The basic prerequisite for induction of adequate treatment volumes for clinical use was the development of a thermostable application system. In an ex vivo test series, the specially developed application system (diffuser tip) with 5760 J had a higher thermic loading capacity than the Ringmode applicator with 4200 J, thus enabling the induction of significantly larger lesions with a volume of 7.6 cm3. The results of a further in vivo test series demonstrated that the lesions were subject to a four-phase connective-tissue organization within a 6-month period. Furthermore, the same laser energy (4200 J) was associated with a significantly lower lesion volume of 2.5 cm3 in the in vivo than in the ex vivo test series. The influence of liver perfusion on the inducible lesion volume was examined in a further animal experimental study. By temporarily interrupting hepatic blood perfusion (Pringle's maneuver) during laser application, the effective volume could be increased to 50.3 cm3 (P < 0.01) using an optical beam splitter. These results show that the technical prerequisites for reliable clinical application of laser-induced thermotherapy have been fulfilled.

Animals↗
PubMed1998

Laser-induced thermotherapy for the treatment of liver metastasis. Correlation of gadolinium-DTPA-enhanced MRI with histomorphologic findings to determine criteria for follow-up monitoring.

PURPOSE: To evaluate gadolinium (Gd)-diethylenetriamine-pentaacetic-acid (DTPA)-enhanced magnetic resonance imaging (MRI) for follow-up monitoring of laser-induced thermotherapy (LITT) and to determine a useful examination schedule. METHODS: LITT of the liver was performed in 55 rabbits using a neodymium: yttrium-aluminum-garnet (Nd:YAG) laser (4-W power output, 840-s exposure time). Gd-DTPA MRI and histologic examinations were performed at different times (0-168 days). RESULTS: Laser-induced lesions underwent regeneration and volume size reduction (69% after 168 days). The correlation coefficient (MR vs. macroscopic analysis) for the mean lesion diameter was r = 0.96. Histology of lesions comprised the four zones that correlated best with MRI findings. Coagulation necroses immediately after LITT was seen as an area of no enhancement on Gd-DTPA MRI. Circular enhancement was first seen 72-96 h after LITT, which was due to early mesenchymal proliferation. CONCLUSIONS: Gd-DTPA MRI is a good monitoring procedure for LITT. MRI should be performed 24 and 96 h after LITT.

Animals↗
PubMed1998

Double-blind multicenter study comparing alprostadil alpha-cyclodextrin with moxisylyte chlorhydrate in patients with chronic erectile dysfunction.

PURPOSE: We compared the efficacy and safety of alprostadil alpha-cyclodextrin and moxisylyte chlorhydrate to induce erections adequate for sexual intercourse in a prospective, randomized, parallel double-blind study in patients with erectile dysfunction. MATERIALS AND METHODS: A total of 156 men with erectile dysfunction due to organic, nonorganic and mixed origin was randomized into 2 parallel treatment groups receiving titrations of an individual optimum dose of alprostadil alpha-cyclodextrin or moxisylyte chlorhydrate. Erectile response was measured by the buckling test. A positive test was associated with axial erection rigidity that did not buckle/deform to 1.0 kg. load. The buckling test was repeated every 10 minutes for up to 60 minutes. RESULTS: A total of 56 patients (75%) in the alprostadil alpha-cyclodextrin group and 32 patients (40%) in the moxisylyte chlorhydrate group responded with at least 1 positive buckling test during the office period. Investigators assessed erections after alprostadil alpha-cyclodextrin to be adequate for sexual intercourse in 61 patients (81%) compared to 37 patients (46%) after moxisylyte chlorhydrate. All efficacy parameters in office reached statistical significance of p < 0.001 in favor of alprostadil alpha-cyclodextrin. During self-injection therapy at home 58 patients (85%) reported at least 1 rigid erection after alprostadil alpha-cyclodextrin compared to 37 patients (61%) after moxisylyte chlorhydrate. Patient and partner opinion of treatment achieved statistically significantly better scores in the alprostadil alpha-cyclodextrin group compared to the moxisylyte chlorhydrate group. CONCLUSIONS: Alprostadil alpha-cyclodextrin is significantly more effective than moxisylyte chlorhydrate in producing full penile rigidity in office and at home. Injection related side effects occur with the same frequency but moxisylyte results in more systemic side effects and alprostadil results in more painful and prolonged erections. Patients and partners are significantly more satisfied with alprostadil alpha-cyclodextrin.

Adrenergic alpha-Antagonists↗
PubMed1998

Visualization of specific angiotensin II binding sites in the rat limbic system.

The present study examined the distribution of angiotensin-binding cells by using a fluorescence-coupled angiotensin II in fixed horizontal sections that contained several limbic structures. In normal female rats, dense staining was found in the CA3 and CA1 regions and the dentate gyrus of the hippocampus--in the subiculum as well as in the entorhinal cortex and piriform cortex. Moderate staining was found in the CA2 region, in the central and medial nuclei of the amygdala. Low-level staining was obtained in the basolateral and lateral nucleus of the amygdala as well as in the bed nucleus of the stria terminalis. The co-incubation of fluorescence-coupled angiotensin II together with angiotensin II in excess and with saralasin, respectively, suppressed the angiotensin staining in structures investigated.

Amygdala↗
PubMed1998

Very slow oscillatory activities in lateral geniculate neurons of freely moving and anesthetized rats.

In urethane anesthetized rats many lateral geniculate neurons display a strong very slow oscillatory behavior in the range of 0.025-0.01 Hz. One of the aims of the present study was to determine whether very slow oscillatory activity in this range can also be obtained in barbiturate anesthetized and in awake animals, respectively. Although very slow oscillations were found in geniculate neurons both during awakeness and during anesthesia, significant differences in peak frequencies of oscillations under the three experimental conditions (barbiturate, urethane, awake) were demonstrated. In addition, we have tested the influence of glutamate antagonists and GABA agonists as well as antagonists on the very slow oscillatory activity in urethane anesthetized rats. Very slow oscillatory activity which could be blocked by the continuous illumination of the eyes was re-induced by iontophoresis of NMDA and non-NMDA glutamate antagonists. GABA(A) as well as GABA(B) agonists also caused a significant re-induction of very slow oscillatory activity under light conditions. In the dark, muscimol, a GABA(A) agonist, significantly enhanced the very slow oscillatory activity, i.e. muscimol either induced it or reduced the frequency of very slow oscillations. For the whole sample, GABA antagonists did not have a significant influence on the very slow oscillatory activity. Autocorrelation analysis based on the spike interval histograms and determination of the spectrum of autocorrelograms revealed the significance of periodicity.

Anesthesia↗
PubMed1998

Angiotensin II inhibits long-term potentiation within the lateral nucleus of the amygdala through AT1 receptors.

Long-term potentiation (LTP) of field potentials in the lateral nucleus of the amygdala (LA) evoked by brief tetanic stimuli of the LA were observed in horizontal rat brain slices. The amplitude of field potentials was significantly enhanced after repetitive stimulation. When angiotensin II was administrated the induction of LTP was suppressed. This inhibition of LTP was mediated by angiotensin II because it could be blocked by the coadministration of saralasin, an nonspecific angiotensin II antagonist. The coadministration of losartan, a competitive antagonist of the AT1 receptor subtype, concomitant with angiotensin II was also able to block this inhibition. The coadministration of the AT2 receptor antagonist PD 123,319 failed to block the inhibition of LTP.

Amygdala↗
PubMed1998

Community health centres in Canada.

In an increasing trend, clients are being moved from tertiary and secondary care to primary care. This "down-loading", accompanied by the increasingly complex needs of clients, has forced providers and policy makers to acknowledge the importance of primary care. In exploring options for the reorganization of primary care, the characteristics of community health centres are often promoted as the model with the best potential. This article outlines a descriptive overview of community health centres (CHCs) across Canada.

Canada↗
PubMed1998

Technology for in situ ablation by laparoscopic and image-guided interstitial laser hyperthermia.

The technical requirements have been fulfilled for the reliable clinical application of laser-induced thermotherapy for treating liver tumors. Laparotomy as well as percutaneous and laparoscopic access modes are available for this method. Thus, laser-induced thermotherapy is a true minimally invasive procedure for treating liver metastases. Presently, it is not possible to make a final assessment on the prognostic value of laser-induced thermotherapy in the treatment of liver tumors. However, recently published data justify the scheduling of a randomized study comparing laser-induced thermotherapy with standard surgical liver resection. In this article, thermobiological and technical principles as well as the different types of application modes for this method are described.

Humans↗