Modification of a commercial atomic force microscopy for low-noise, high-resolution frequency-modulation imaging in liquid environment

A key issue for high-resolution frequency-modulation atomic force microscopy imaging in liquids is minimizing the frequency noise, which requires a detailed analysis of the corresponding noise contributions. In this paper, we present a detailed description for modifying a commercial atomic force microscope (Bruker MultiMode V with Nanoscope V controller), aiming at atomic-resolution frequency-modulation imaging in ambient and in liquid environment. Care was taken to maintain the AFMs original stability and ease of operation. The new system builds upon an optimized light source, a new photodiode and an entirely new amplifier. Moreover, we introduce a home-built liquid cell and sample holder as well as a temperature-stabilized isolation chamber dedicated to low-noise imaging in liquids. The success of these modifications is measured by the reduction in the deflection sensor noise density from initially 100 fm/√Hz to around 10 fm/√Hz after modification. The performance of our instrument is demonstrated by atomically resolved images of calcite taken under liquid conditions.

Knockdown of the gene encoding Drosophila tribbles homologue 3 (Trib3) improves insulin sensitivity through peroxisome proliferator-activated receptor-γ (PPAR-γ) activation in a rat model of insulin resistance

AIMS/HYPOTHESIS

Insulin action is purportedly modulated by Drosophila tribbles homologue 3 (TRIB3), which in vitro prevents thymoma viral proto-oncogene (AKT) and peroxisome proliferator-activated receptor-γ (PPAR-γ) activation. However, the physiological impact of TRIB3 action in vivo remains controversial.

METHODS

We investigated the role of TRIB3 in rats treated with either a control or Trib3 antisense oligonucleotide (ASO). Tissue-specific insulin sensitivity was assessed in vivo using a euglycaemic-hyperinsulinaemic clamp. A separate group was treated with the PPAR-γ antagonist bisphenol-A-diglycidyl ether (BADGE) to assess the role of PPAR-γ in mediating the response to Trib3 ASO.

RESULTS

Trib3 ASO treatment specifically reduced Trib3 expression by 70% to 80% in liver and white adipose tissue. Fasting plasma glucose, insulin concentrations and basal rate of endogenous glucose production were unchanged. However, Trib3 ASO increased insulin-stimulated whole-body glucose uptake by ~50% during the euglycaemic-hyperinsulinaemic clamp. This was attributable to improved skeletal muscle glucose uptake. Despite the reduction of Trib3 expression, AKT2 activity was not increased. Trib3 ASO increased white adipose tissue mass by 70% and expression of Ppar-γ and its key target genes, raising the possibility that Trib3 ASO improves insulin sensitivity primarily in a PPAR-γ-dependent manner. Co-treatment with BADGE blunted the expansion of white adipose tissue and abrogated the insulin-sensitising effects of Trib3 ASO. Finally, Trib3 ASO also increased plasma HDL-cholesterol, a change that persisted with BADGE co-treatment.

CONCLUSIONS/INTERPRETATION

These data suggest that TRIB3 inhibition improves insulin sensitivity in vivo primarily in a PPAR-γ-dependent manner and without any change in AKT2 activity.

Differing in vitro biology of equine, ovine, porcine and human articular chondrocytes derived from the knee joint: an immunomorphological study

For lack of sufficient human cartilage donors, chondrocytes isolated from various animal species are used for cartilage tissue engineering. The present study was undertaken to compare key features of cultured large animal and human articular chondrocytes of the knee joint. Primary chondrocytes were isolated from human, porcine, ovine and equine full thickness knee joint cartilage and investigated flow cytometrically for their proliferation rate. Synthesis of extracellular matrix proteins collagen type II, cartilage proteoglycans, collagen type I, fibronectin and cytoskeletal organization were studied in freshly isolated or passaged chondrocytes using immunohistochemistry and western blotting. Chondrocytes morphology, proliferation, extracellular matrix synthesis and cytoskeleton assembly differed substantially between these species. Proliferation was higher in animal derived compared with human chondrocytes. All chondrocytes expressed a cartilage-specific extracellular matrix. However, after monolayer expansion, cartilage proteoglycan expression was barely detectable in equine chondrocytes whereby fibronectin and collagen type I deposition increased compared with porcine and human chondrocytes. Animal-derived chondrocytes developed more F-actin fibers during culturing than human chondrocytes. With respect to proliferation and extracellular matrix synthesis, human chondrocytes shared more similarity with porcine than with ovine or equine chondrocytes. These interspecies differences in chondrocytes in vitro biology should be considered when using animal models.

Neural, electrodermal and behavioral response patterns in contingency aware and unaware subjects during a picture-picture conditioning paradigm

One way of investigating affective learning is the use of aversive pictures as unconditioned stimuli (UCS) in conditioning paradigms. In the last decades, there has been a heated debate on the influence of contingency awareness on conditioned responses (CRs). Only a few studies found CRs in contingency unaware subjects whereas other studies only reported conditioned reactions in contingency aware participants. However, as a shortcoming, most studies employing picture-picture paradigms only investigated one response level (e.g. changes in subjective ratings). Further, changes in brain activity have so far been neglected in this field of research. The aim of the present study was to investigate different response levels with respect to contingency awareness: brain activity measured by functional magnetic resonance imaging (fMRI), skin conductance responses (SCRs) and valence ratings. A neutral geometric shape (conditioned stimulus, CS+) was followed by aversive pictures, whereas another shape (CS-) preceded neutral pictures. Unaware participants showed CRs in brain activity (e.g. the insula). Generally more activity was observed in the fear network (e.g. the amygdala, the lateral orbitofrontal cortex) in aware participants and in the nucleus accumbens (NAcc). Investigation of SCRs and valence ratings revealed that only aware participants showed conditioned reactions. Our results point toward dissociations between response levels (e.g. brain activity) not affected by contingency awareness and more cognitive response levels (e.g. subjective ratings and SCRs) which are affected by contingency awareness. As a unique finding in human aversive conditioning, we discuss the role of the nucleus accumbens as well as practical implications for affective learning models.

Pathogenicity ofMycoplasma lipofaciensstrain ML64, isolated from an egg of a Northern Goshawk (Accipiter gentilis), for chicken embryos

Some Mycoplasma species are well-known avian pathogens and are of importance in poultry breeder flocks due to their pathogenic potential for embryos. Mycoplasmas are regularly detected in birds of prey, and a strain of Mycoplasma lipofaciens that was isolated from an egg of a Northern Goshawk (Accipiter gentilis) was examined for its pathogenicity in specific pathogen free chicken embryos since birds of prey eggs were not available for this purpose. The strain was found to be pathogenic, causing a high mortality as well as dwarfing, curled toes and infiltrations of heterophils in the liver, kidney, intestine and chorioallantoic membrane.

ESCI Award 2006. Mitochondrial function and endocrine diseases

Mitochondria are fundamental for oxidative energy production and impairment of their functionality can lead to reduced ATP synthesis and contribute to initiation of apoptosis. Endocrine tissues critically rely on oxidative phosphorylation so that mitochondrial abnormalities may either be causes or consequences of diminished hormone production or action. Abnormalities typical for diseases caused by mitochondrial DNA mutations such as Kearns-Sayre syndrome or mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes syndrome are also seen in certain endocrine diseases. Lack or excess of thyroid hormones, major ubiquitous regulators of mitochondrial content and activity, cause muscular abnormalities and multisystem disorders. Mitochondria are a further prerequisite for steroidogenesis as well as insulin secretion and action. Recent studies showed that reduced mitochondrial ATP synthesis in skeletal muscle is a feature of certain hereditary and acquired forms of insulin resistance and diabetes mellitus. Finally, ageing is not only accompanied by various degrees of hormonal deficiency and insulin resistance but is also associated with a progressive decline of mitochondrial number and function. Future research is needed to examine whether mitochondrial abnormalities are the cause or consequence of ageing and frequent metabolic diseases such as obesity and type 2 diabetes mellitus, and to address mitochondria as a target for novel therapeutic regimes.

Development of neuropathy in patients (pts) with multiple myeloma (MM) treated with thalidomide (thal)—Patterns of occurrence and the role of electrophysiologic monitoring

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Background: Given new treatment options for pts with MM, physicians are faced with the dilemma of how best to sequence these drugs in order to optimize efficacy and toxicity. Peripheral neuropathy frequently limits the duration of treatment (Rx) with thal. In this study we assessed the utility of serial nerve electrophysiological studies (NES) to detect the onset of neuropathy, and assessed the time course of occurrence and possible clinical and Rx-related predictive factors. Methods: 75 pts with relapsed/refractory MM were enrolled in a multi-centre trial of thal. In addition to clinical assessment, pts underwent sensory and motor NES at baseline and every 3 months in order to identify neuropathy. We examined the value of baseline and serial NES for development of neuropathy, with time to development of neuropathy according to clinical or NES criteria compared using Kaplan-Meier analysis. Differences between pt and Rx-related variables were compared using a Mann-Whitney U-test or a Fisher’s exact test. Results: Thirty nine percent had some NES abnormalities at baseline. Pts were treated with thal at a median dose intensity of 373 mg/day and followed for a median of 18 months (range 6–26). Thirty-one of the 75 pts (41%) developed neuropathy during thal Rx, with 11 (15%) ceasing thal due to neuropathy. The actuarial incidence of any neuropathy increased from 38% at 6 months to 73% at 12 months with 81% of responding pts developing this complication. The use of NES did not reliably predict the imminent development of clinical neuropathy requiring cessation of thal. Nor were pt age, gender or type of prior therapy (ie vincristine) predictive. Development of neuropathy was related to duration of thal exposure with a median time of 268 days thal in those who developed neuropathy compared to 89 days in those who did not (p = 0.0001). Cumulative dose or dose intensity received were not predictive. Conclusions: The majority of pts will develop peripheral neuropathy given sufficient length of thal Rx and to minimize the risk of neurotoxicity, therapy should be limited to less than six months. NES monitoring provides no clear benefit over careful clinical evaluation for the development of clinically significant neuropathy.

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Molecular epidemiology of Salmonella enterica serovar Agona: characterization of a diffuse outbreak caused by aniseed-fennel-caraway infusion

During 2002-2003 increased numbers of notified salmonellosis due to S. enterica serovar Agona were observed in Germany. In order to understand the recent spread of this serovar and to trace the route of infection to its source, a new phage-typing scheme and pulsed field gel electrophoresis (PFGE) were used to analyse these isolates. By using 14 bacteriophages, 52 phage types were distinguished among the S. Agona strains. PFGE also differentiated 52 different patterns. A combination of both methods generated 94 clonal types among 165 S. Agona strains originating from Germany and other countries including the United States, United Arab Emirates, Turkey, India, Austria and Finland, indicating a great biological diversity within this serovar. However, 36 recent S. Agona isolates from infantile gastroenteritis in Germany, from an untreated batch of aniseed imported from Turkey and from fennel-aniseed-caraway infusion (packed in tea bags) revealed clonal identity indicating their epidemiological relatedness as a new source of infection. It is suggested that strains of S. Agona will continue to be of public health concern, and that phage typing together with PFGE typing should be applied as reliable and rapid tools for epidemiological subtyping and future monitoring.