Wider die blanke Ohnmacht der Lehrer : was tun mit Schülern, die als nicht schulfähig gelten?

Rezension zu: Thomas von Freyberg, Angelika Wolff (Hrsg.) : Störer und Gestörte – Konfliktgeschichten nicht beschulbarer Jugendlicher Band 1, Verlag Brandes & Apsel, Frankfurt 2005, ISBN 3-86099-813-7, 317 Seiten, 24,90 Euro

Adhesion of oral streptococci to enamel and dental materials : studies using a flow chamber and microcalorimetry

Dental plaque formation on human teeth is the crucial etiologic factor in the pathogenesis of oral diseases: caries, periodontal diseases, and peri-implantitis. Dental plaque has been defined as a diverse community of microorganisms found on teeth as a biofilm, embedded in an extracellular polymer matrix of bacterial origin and including host components. Bacterial colonization starts with the adhesion of early colonizers, called pioneer bacteria, to the salivary pellicle on teeth as well as on dental materials within minutes after tooth cleaning. The early colonizers, mostly streptococcoci, contribute to plaque development and ultimately to oral diseases. Investigations of dental plaque, including bacterial adhesion, employ various in vivo and in vitro models and use microscopic methods to assess surface phenomena. The complexity of the oral environment makes it difficult to generate an in vitro system including all relevant aspects. The studies presented (paper I-III) were aimed to adapt two in vitro models, a flow chamber system and a microcalorimetric technique, for investigating adhesion of oral streptococci to human enamel, glass and different dental materials. The dental materials used for the flow chamber experiments (paper I + II) were titanium (Rematitan®M), gold (Neocast 3), ceramic (Vita Omega 900), composite (Tetric Ceram), and four different all-ceramics. The early colonizing Streptococcus sanguinis, S. oralis, and the caries-inducing S. mutans, and S. sobrinus were used as the model organisms. The saliva-coated materials were incubated with the bacteria in the flow chamber during one hour. Number and vitality of adhering bacteria were determined microscopically after staining. The results suggested that variations in the number and vitality of the adherent oral streptococci depend on the surface characteristics of the substrata and the acquired salivary pellicle. It also depended on the bacterial species, as S. mutans and S. sobrinus adhered about 10 x less than S. sanguinis and S. oralis. Isothermal Microcalorimetry (paper III) indeed allowed evaluation of initial bacterial adhesion of S. sanguinis to glass. Maximum heat flow measurements during adhesion were about 10 fold lower than during bacterial growth. Experiments showed that increased surface areas, provided by increased amounts of glass beads, were associated with higher energy release. Heat flow was higher when cells were suspended in human saliva than in PBS. Based on these results both methods appear to be applicable to study bacterial adhesion to new dental restorative or implant materials. Advantages and disadvantages of the methods are discussed

Investigation of coagulation and serum biochemistry profiles in dairy cattle with different degrees of fatty liver

The aim of the present study was to investigate clotting profiles, plasma biochemical, and hematological parameters in cows with different degrees of fatty liver. The degree of fatty liver was determined based on histopathology of liver biopsies. Fifty cows referred for left displacement of the abomasum and different degrees of fatty liver were investigated. A clotting profile including prothrombin time (PT), thrombin time (TT), activated partial thromboplastin time (aPTT), and fibrinogen did not reveal differences between cows with or without fatty liver. Aspartate aminotransferase (ASAT) was the only biochemical parameter being significantly different in cows with fatty liver. The activity of ASAT could not differentiate any stage of fatty liver. Our findings demonstrate that alterations in clotting profiles in dairy cows are not related to fatty liver. Biochemical parameters are not sufficient to determine the severity of fatty liver

Adhesion of oral streptococci to all-ceramics dental restorative materials invitro

In recent years, patients have benefited from the development of better and more esthetic materials, including all-ceramics dental restorative materials. Dental plaque formation on teeth and restorative materials plays an important role in the pathogenesis of oral diseases. This study investigates initial adhesion of stationary phase streptococcal species to different all-ceramics dental restorative materials. The saliva-coated materials were incubated with the bacteria for 1h in an invitro flow chamber which mimics environmental conditions in the oral cavity. Number and vitality of adhering bacteria were determined microscopically after staining. Surface roughness and the composition of the materials had no distinctive influence on bacterial adhesion. However, S.mutans and S.sobrinus adhered about tenfold less numerous to all materials than the other streptococcal species. Further, there was a correlation between bacterial vitality and materials' glass content. The results showed that early plaque formation was influenced predominantly by the presence of the salivary pellicle rather than by material dependent parameters whereas the composition of the all-ceramics appeared to have influenced the percentage of viable cells during the adhesion process. This presented invitro technique may provide a useful model to study the influence of different parameters on adherence of oral streptococcal specie

Nanofluidic systems for individual and contact-free electrostatic trapping of charged objects

Contact-free trapping of nano-objects in solution is of broad interest for many applications, such as studying of polymer dynamics, detecting molecular reactions or investigating the structure and functionality of large biomolecules, to name a few. Although several trapping methods have been developed, stable and high-throughput trapping of individual nanometer-sized objects in a straightforward manner remain challenging. A powerful method of trapping charged objects smaller than 100 nm and without any external applied power is geometry-induced electrostatic (GIE) trapping. This method is based on altering the surface topography of nanofluidic channels that are charged when exposed to water. The topographically modified surfaces result in electrostatic potential wells, in which nano-objects can be trapped from milliseconds to several days, depending on the trap specification and the buffer solution. Various trapping geometries (e.g., circular pockets and rectangular slits or grids) can be realized using state-of-the-art nanofabrication tools. This thesis explores the development and use of nanofluidic devices for electrostatic trapping and manipulation of nano-objects, such as gold nanoparticles (Au NPs) or DNA. For imaging the Au NPs, a home built interferometric scattering (iSCAT) detection system was used. iSCAT is a label free coherent optical microscopy technique that significantly increases the signal-to-noise ratio (SNR) in comparison to other imaging methods that are based on detecting only the signal scattered by a nano-object. In detail, using standard silicon-based GIE trapping devices, Au NPs smaller than 60 nm become difficult to detect using iSCAT microscopy. To overcome this limitation, trapping devices made from glass substrate are introduced with a new developed fabrication process. These devices allow imaging of Au NPs with an increased contrast and SNR of an order of magnitude using iSCAT detection, enabling the detection of relatively smaller nanoparticles and thereby allowing the study of their trapping behavior. Further, the GIE trapping method is integrated into a microfluidic system that comes with the key benefits of reduced sample volume, in situ change of solutions, precise control of solution delivery, and the feasibility to trap nano-objects along a gradient of e.g. salt or other reactants. Using this high-throughput screening device, the performance has been quantitatively analyzed by screening the electrostatic potential along a salt gradient using 60 nm Au NPs as probes in a single experiment. Additionally, the critical salt concentration for the stability of the colloidal dispersion could be observed. The advancement of this method sets the ground for a variety of new experiments. As an example, having the possibility to insert and flush the device with different solutions, functionalization of the nanofluidic channel walls with positively charged polyelectrolytes was achieved resulting in a reversal of the walls net charge and thus allowing the trapping of positively charged Au NPs. One drawback that makes the development and application of GIE trapping devices made from rigid SiOx materials difficult, is the high cost and time-consuming nanofabrication in limiting infrastructures such as cleanroom facilities. Hence, new GIE trapping devices made from the soft material polydimethylsiloxane (PDMS) are introduced that are fabricated using a high-throughput and easy handling replica molding process. Stable trapping of Au NPs down to 60 nm in diameter is demonstrated and potential depths of up to Q ~ 24 kBT of circular pockets are experimentally observed that provide stable trapping for many days. In addition, by taking advantage of the feature that PDMS is a flexible material, the PDMS devices are elastically compressed, which results in a reduction of the device channel height and thus active tuning of trapping strengths and residence times. With this capability, extremely deep potentials of up to Q ~ 200 kBT are achieved, providing practically permanent contact-free trapping of individual nano-objects. Furthermore, the implementation of a 3D PDMS pneumatic valve system is demonstrated, which makes the devices capable of controlling the trap stiffnesses and residence times actively as well as trapping and releasing the nano-objects. These devices will enable high-throughput trapping of nano-objects for studying their behavior and interactions in aqueous environment. The simple and low-cost fabrication process and the fact that the chip-based devices do not need externally applied fields or an elaborate build-up will make them equally available for research and commercial applications

Duodenal ileus caused by a calf feeding nipple in a cow

<p>Abstract</p> <p>Background</p> <p>The aim of this report was to describe duodenal obstruction caused by a rubber foreign body in a cow.</p> <p>Case Presentation</p> <p>The clinical, biochemical and ultrasonographic findings in a five-year-old Swiss Braunvieh cow with duodenal ileus caused by a calf feeding nipple are described. The main clinical signs were anorexia, ruminal tympany, decreased faecal output and abomasal reflux syndrome. Ultrasonographic examination revealed reticular hyperactivity and a dilated duodenum. A diagnosis of duodenal ileus was made and the cow underwent right-flank laparotomy, which revealed a dilation of the cranial part of the duodenum because of obstruction by a pliable foreign body. This was identified via enterotomy as a calf feeding nipple. The cow was healthy at the time of discharge four days after surgery and went on to complete a successful lactation.</p> <p>Conclusions</p> <p>To our knowledge, this is the first description of duodenal obstruction by a calf feeding nipple. This is an interesting case, which broadens the spectrum of the causes of duodenal ileus, which is usually caused by obstruction of the duodenum by a phytobezoar.</p

Duodenal ileus caused by a calf feeding nipple in a cow

Background: The aim of this report was to describe duodenal obstruction caused by a rubber foreign body in a cow. Case Presentation: The clinical, biochemical and ultrasonographic findings in a five-year-old Swiss Braunvieh cow with duodenal ileus caused by a calf feeding nipple are described. The main clinical signs were anorexia, ruminal tympany, decreased faecal output and abomasal reflux syndrome. Ultrasonographic examination revealed reticular hyperactivity and a dilated duodenum. A diagnosis of duodenal ileus was made and the cow underwent rightflank laparotomy, which revealed a dilation of the cranial part of the duodenum because of obstruction by a pliable foreign body. This was identified via enterotomy as a calf feeding nipple. The cow was healthy at the time of discharge four days after surgery and went on to complete a successful lactation. Conclusions: To our knowledge, this is the first description of duodenal obstruction by a calf feeding nipple. This is an interesting case, which broadens the spectrum of the causes of duodenal ileus, which is usually caused by obstruction of the duodenum by a phytobezoar

Small intestinal volvulus in 47 cows

OBJECTIVE: To describe the findings, treatment, and outcome of small intestinal volvulus (SIV) in 47 cows. ANIMALS AND PROCEDURE: Retrospective analysis of medical records. Comparison of the findings for 18 surviving and 29 non-surviving cows. RESULTS: The most common abnormal vital signs were tachycardia (68.0%), tachypnea (59.6%), and decreased rectal temperature (51.1%). Signs of colic occurred in 66.0% of cows in the study. Rumen motility was reduced or absent in 93.6% of cows, and intestinal motility in 76.6%. Clinical signs on ballottement and/or percussion and simultaneous auscultation were positive on the right side in 78.7% of cows. Transrectal examination showed dilated small intestines in 48.9% of cows. The rectum contained little or no feces in 93.6% of cows. The principal laboratory abnormalities were hypocalcemia (74.1%), hypokalemia (73.8%), azotemia (62.8%), hypermagnesemia (61.6%), and hemoconcentration (60.0%). The principal ultrasonographic findings were dilated small intestines (87.1%) and reduced or absent small intestinal motility (85.2%). Forty-one of the 47 cows underwent right flank laparotomy and the SIV was reduced in 21 cows. When comparing the clinical and laboratory findings of 18 surviving and 29 non-surviving cows, the groups differed significantly with respect to severely abnormal general condition (16.7 versus 37.9%), rumen stasis (22.2 versus 79.3%), intestinal atony (16.7 versus 48.3%), serum urea concentration (6.5 versus 9.8 mmol/L), and serum magnesium concentration (0.98 versus 1.30 mmol/L). In summary, 38.3% of the cows were discharged and 61.7% were euthanized before, during, or after surgery. CONCLUSION AND CLINICAL RELEVANCE: An acute course of disease, little or no feces in the rectum, and dilated small intestines were characteristic of SIV in this study population