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Biomedical subjects

N Brenner

Publications and source records attributed to N Brenner.

12 recordsLinked to original sources
PubMed2005

Primary neuroendocrine carcinoma of inguinal lymph node.

Ninety-seven percent of neuroendocrine carcinomas are located in the gastrointestinal tract or in the bronchopulmonary tree. Inguinal lymph nodes as the primary tumor site for neuroendocrine carcinoma represent a very unusual location, and have only been described in 2 patient series in the literature. A 64-year-old, previously healthy, Caucasian female presented with a 2-month history of an enlarged inguinal lymph node on the right side. The removed lymph node showed histological and immunohistochemical characteristics of neuroendocrine differentiation (positive for synaptophysin, cytokeratin 20, neuron-specific enolase and chromogranin A). Although extensive investigations including repeated CT and NMR scans, classical endoscopy, wireless capsule endoscopy of the small intestine, octreotide- and MIBG scintigraphy were performed, no other primary tumor was found. Furthermore, there was no evidence of Merkel cell carcinoma on dermatological examinations. A possible explanation for the presence of neuroendocrine carcinomas within the lymph nodes is malignant transformation of preexisting intranodal epithelial nests, which have previously been described in lymph nodes located close to the salivary glands, thyroid gland, breast tissue and pancreas. Since the surgical removal of the affected lymph node, the patient has now been disease-free for 42 months. We therefore consider our case to represent a primary undifferentiated neuroendocrine carcinoma in an inguinal lymph node.

Carcinoma, Neuroendocrine↗
PubMed2004

[Special aspects of implant-associated infection in orthopedic surgery. From the pathophysiology to custom-tailored prevention strategies].

One of the most important risk factors in orthopedic surgery is implant-associated infection. Adhesion and colonization mediated implant infections are extremely resistant to antibiotics and host defences and frequently persist until the biomaterial or foreign body is removed, which is standard therapy. Tissue damage caused by surgery and foreign body implantation increases the susceptibility to infections, activates host defences and stimulates the generation of inflammatory mediators including radicals that are further aggravated by bacterial activity and toxins. Nearly one third of implant-related infections can be prevented by strictly following established infection control guidelines. However, a significant number of implant-associated infections remains. The escape of bacteria from host defence and antibiotic therapy makes the development of infection-resistant materials as anti-microbial drug delivery systems feasible. This concept consists of the sustained delivery of antimicrobial drugs into the local microenvironment of implants avoiding systemic side effects exceeding usual systemic concentrations by magnitudes of order.

Anti-Bacterial Agents↗
PubMed2004

Quantification, localization, and expression of IGF-I and TGF-beta1 during growth factor-stimulated fracture healing.

Because of the increasing interest on stimulating fracture healing, knowledge about the role and chronology of growth factors during the healing process is important. The purpose of this study was to quantify the protein concentration of IGF-I and TGF-beta1 during rat tibial fracture healing 5, 10, and 15 days after fracture using ELISA methods and to analyze the distribution of the proteins and the related mRNA expression in the fracture callus by immunohistochemistry and in situ hybridization. The following three groups were analyzed: Fractured tibiae intramedullary stabilized with K-wires coated with IGF-I and TGF-beta1 compared with fractures stabilized with uncoated K-wires and unfractured tibiae. The weight of the callus increased during the healing process in both experimental groups. The protein concentration of IGF-I and TGF-beta1 in the fracture callus showed significant changes between the investigated time points and treatment groups compared with the unfractured tibia. IGF-I increased with healing time whereas TGF-beta1 revealed a constantly elevated level at the investigated time points. Mesenchymal cells, osteoblasts, osteocytes, proliferating and immature chondrocytes, and osteoclasts expressed both growth factors. No differences in the expression and localization pattern of the growth factors were detectable among the groups. Using the different methods for quantification and visualization of the growth factors, no differences (except the increased IGF-I concentration at day 15 in the growth factor group) were seen between the normal and the growth factor-stimulated fracture healing as an indication for physiological healing after exogenous growth factor treatment.

Absorbable Implants↗
PubMed2000

Adaptive rescaling maximizes information transmission.

Adaptation is a widespread phenomenon in nervous systems, providing flexibility to function under varying external conditions. Here, we relate an adaptive property of a sensory system directly to its function as a carrier of information about input signals. We show that the input/output relation of a sensory system in a dynamic environment changes with the statistical properties of the environment. Specifically, when the dynamic range of inputs changes, the input/output relation rescales so as to match the dynamic range of responses to that of the inputs. We give direct evidence that the scaling of the input/output relation is set to maximize information transmission for each distribution of signals. This adaptive behavior should be particularly useful in dealing with the intermittent statistics of natural signals.

Adaptation, Physiological↗
PubMed2000

Synergy in a neural code.

We show that the information carried by compound events in neural spike trains-patterns of spikes across time or across a population of cells-can be measured, independent of assumptions about what these patterns might represent. By comparing the information carried by a compound pattern with the information carried independently by its parts, we directly measure the synergy among these parts. We illustrate the use of these methods by applying them to experiments on the motion-sensitive neuron H1 of the fly's visual system, where we confirm that two spikes close together in time carry far more than twice the information carried by a single spike. We analyze the sources of this synergy and provide evidence that pairs of spikes close together in time may be especially important patterns in the code of H1.

Action Potentials↗
PubMed1995

[Efficacy of Doppler color echography in the diagnosis of caverno-venous leakage in the impotent patient].

Duplex sonography is now the gold standard for the non-invasive study of cavernous arteries. Many authors consider that this technique allows for the exploration of the veno-occlusive system and can detect venous leakage. The most common criteria is an end diastolic velocity > 5 cm/s, measured in the cavernous arteries. In a retrospective study, 34 impotent patients were reviewed. All of them were explored both by doppler sonography and pharmacocavernosometry to assess the efficacy of duplex sonography in detecting venous leakage. The data show that the doppler detects venous leakage in only 41%. The specificity and the sensitivity are both 50% which is clearly disappointing. Therefore, in our experience, duplex sonography is not a reliable technique to detect venous leakage. We consider that the best method is still pharmacocavernosometry.

Arteries↗
PubMed1994

Receptor binding radiotracers for the angiotensin II receptor: radioiodinated [Sar1, Ile8]Angiotensin II.

The potential for imaging the angiotensin II receptor was evaluated using the radioiodinated peptide antagonist [125I][Sar1, Ile8)angiotensin II. The radioligand provides a receptor-mediated signal in several tissues in rat (kidneys, adrenal and liver). The receptor-mediated signal of 3% ID/g kidney cortex should be sufficient to permit imaging, at least via SPECT. The radiotracer is sensitive to reductions in receptor concentration and can be used to define in vivo dose-occupancy curves of angiotensin II receptor ligands. Receptor-mediated images of [123I][Sar1, Ile8]angiotensin II were obtained in the rat kidney and Rhesus monkey liver.

1-Sarcosine-8-Isoleucine Angiotensin II↗
PubMed1981

Retroactive interference in discrimination learning.

In stage 1 of this experiment pigeons were trained to discriminate between two levels of noise or two colors by pecking on one of two disks. In stage 2 the discriminative stimuli were not presented, but pecking on the disks was rewarded on a random schedule. The second procedure caused the pigeons to forget the discrimination they had learned.

Acoustic Stimulation↗