Combined in situ zymography, immunofluorescence, and staining of iron oxide particles in paraffin-embedded, zinc-fixed tissue sections

Superparamagnetic iron oxide particles are used as potent contrast agents in magnetic resonance imaging. In histology, these particles are frequently visualized by Prussian blue iron staining of aldehyde-fixed, paraffin-embedded tissues. Recently, zinc salt-based fixative was shown to preserve enzyme activity in paraffin-embedded tissues. In this study, we demonstrate that zinc fixation allows combining in situ zymography with fluorescence immunohistochemistry (IHC) and iron staining for advanced biologic investigation of iron oxide particle accumulation. Very small iron oxide particles, developed for magnetic resonance angiography, were applied intravenously to BALB/c nude mice. After 3 hours, spleens were explanted and subjected to zinc fixation and paraffin embedding. Cut tissue sections were further processed to in situ zymography, IHC, and Prussian blue staining procedures. The combination of in situ zymography as well as IHC with subsequent Prussian blue iron staining on zinc-fixed paraffin-embedded tissues resulted in excellent histologic images of enzyme activity, protease distribution, and iron oxide particle accumulation. The combination of all three stains on a single section allowed direct comparison with only moderate degradation of fluorescein isothiocyanate-labeled substrate. This protocol is useful for investigating the biologic environment of accumulating iron oxide particles, with excellent preservation of morphology.     

Quantifying the improvement of surrogate indices of hepatic insulin resistance using complex measurement techniques

We evaluated the ability of simple and complex surrogate-indices to identify individuals from an overweight/obese cohort with hepatic insulin-resistance (HEP-IR). Five indices, one previously defined and four newly generated through step-wise linear regression, were created against a single-cohort sample of 77 extensively characterised participants with the metabolic syndrome (age 55.6 ± 1.0 years, BMI 31.5 ± 0.4 kg/m(2); 30 males). HEP-IR was defined by measuring endogenous-glucose-production (EGP) with [6-6(2)H(2)] glucose during fasting and euglycemic-hyperinsulinemic clamps and expressed as EGP*fasting plasma insulin. Complex measures were incorporated into the model, including various non-standard biomarkers and the measurement of body-fat distribution and liver-fat, to further improve the predictive capability of the index. Validation was performed against a data set of the same subjects after an isoenergetic dietary intervention (4 arms, diets varying in protein and fiber content versus control). All five indices produced comparable prediction of HEP-IR, explaining 39-56% of the variance, depending on regression variable combination. The validation of the regression equations showed little variation between the different proposed indices (r(2) = 27-32%) on a matched dataset. New complex indices encompassing advanced measurement techniques offered an improved correlation (r = 0.75, P<0.001). However, when validated against the alternative dataset all indices performed comparably with the standard homeostasis model assessment for insulin resistance (HOMA-IR) (r = 0.54, P<0.001). Thus, simple estimates of HEP-IR performed comparable to more complex indices and could be an efficient and cost effective approach in large epidemiological investigations.     

Persistence versus escape: Aspergillus terreus and Aspergillus fumigatus employ different strategies during interactions with macrophages

Invasive bronchopulmonary aspergillosis (IBPA) is a life-threatening disease in immunocompromised patients. Although Aspergillus terreus is frequently found in the environment, A. fumigatus is by far the main cause of IBPA. However, once A. terreus establishes infection in the host, disease is as fatal as A. fumigatus infections. Thus, we hypothesized that the initial steps of disease establishment might be fundamentally different between these two species. Since alveolar macrophages represent one of the first phagocytes facing inhaled conidia, we compared the interaction of A. terreus and A. fumigatus conidia with alveolar macrophages. A. terreus conidia were phagocytosed more rapidly than A. fumigatus conidia, possibly due to higher exposure of β-1,3-glucan and galactomannan on the surface. In agreement, blocking of dectin-1 and mannose receptors significantly reduced phagocytosis of A. terreus, but had only a moderate effect on phagocytosis of A. fumigatus. Once phagocytosed, and in contrast to A. fumigatus, A. terreus did not inhibit acidification of phagolysosomes, but remained viable without signs of germination both in vitro and in immunocompetent mice. The inability of A. terreus to germinate and pierce macrophages resulted in significantly lower cytotoxicity compared to A. fumigatus. Blocking phagolysosome acidification by the v-ATPase inhibitor bafilomycin increased A. terreus germination rates and cytotoxicity. Recombinant expression of the A. nidulans wA naphthopyrone synthase, a homologue of A. fumigatus PksP, inhibited phagolysosome acidification and resulted in increased germination, macrophage damage and virulence in corticosteroid-treated mice. In summary, we show that A. terreus and A. fumigatus have evolved significantly different strategies to survive the attack of host immune cells. While A. fumigatus prevents phagocytosis and phagolysosome acidification and escapes from macrophages by germination, A. terreus is rapidly phagocytosed, but conidia show long-term persistence in macrophages even in immunocompetent hosts.     

Altered velocity processing in schizophrenia during pursuit eye tracking

Smooth pursuit eye movements (SPEM) are needed to keep the retinal image of slowly moving objects within the fovea. Depending on the task, about 50%-80% of patients with schizophrenia have difficulties in maintaining SPEM. We designed a study that comprised different target velocities as well as testing for internal (extraretinal) guidance of SPEM in the absence of a visual target. We applied event-related fMRI by presenting four velocities (5, 10, 15, 20°/s) both with and without intervals of target blanking. 17 patients and 16 healthy participants were included. Eye movements were registered during scanning sessions. Statistical analysis included mixed ANOVAs and regression analyses of the target velocity on the Blood Oxygen Level Dependency (BOLD) signal. The main effect group and the interaction of velocity×group revealed reduced activation in V5 and putamen but increased activation of cerebellar regions in patients. Regression analysis showed that activation in supplementary eye field, putamen, and cerebellum was not correlated to target velocity in patients in contrast to controls. Furthermore, activation in V5 and in intraparietal sulcus (putative LIP) bilaterally was less strongly correlated to target velocity in patients than controls. Altered correlation of target velocity and neural activation in the cortical network supporting SPEM (V5, SEF, LIP, putamen) implies impaired transformation of the visual motion signal into an adequate motor command in patients. Cerebellar regions seem to be involved in compensatory mechanisms although cerebellar activity in patients was not related to target velocity.     

COMP-angiopoietin-1 recovers molecular biomarkers of neuropathy and improves vascularisation in sciatic nerve of ob/ob mice

Background

Leptin-deficient ob/ob mice are a model of type 2 diabetes induced peripheral neuropathy. Ob/ob mice exhibit obesity, insulin resistance, hyperglycaemia, and alterations of peripheral nerve fibres and endoneural microvessels. Here we test the hypothesis that cartilage oligomeric matrix protein (COMP)-Ang-1, a soluble and stabile form of Ang-1 which promotes angiogenesis and nerve growth, improves regeneration of nerve fibres and endoneural microvessels in ob/ob mice.

Methods and Findings

COMP-Ang-1 (100 ng/ml) or NaCl were intraperitoneally (i.p.) injected into male (N = 184), 3-month old, ob/ob or ob/+ mice for 7 and 21 days. We measured expression of Nf68, GAP43, Cx32, Cx26, Cx43, and TNFα in sciatic nerves using Western blot analysis. To investigate the inflammation in sciatic nerves, numbers of macrophages and T-cells were counted after immunofluorescence staining. In ultrathin section, number of myelinated/non-mylinated nerve fibers, g-ratio, the thickness of Schwann cell basal lamina and microvessel endothelium were investigated.Endoneural microvessels were reconstructed with intracardial FITC injection. Treatment with COMP-Ang-1 over 21 days significantly reduced fasting blood glucose and plasma cholesterol concentrations compared to saline treated ob/ob mice. In addition, COMP-Ang-1 treatment: 1) up-regulated expression of Nf68 and GAP43; 2) improved expression of gap junction proteins including connexin 32 and 26; 3) suppressed the expression of TNFα and Cx43 and 4) led to decreased macrophage and T-cell infiltration in sciatic nerve of ob/ob mice. The significant changes of sciatic nerve ultrastructure were not observed after 21-day long COMP-Ang-1 treatment. COMP-Ang-1 treated ob/ob mice displayed regeneration of small-diameter endoneural microvessels. Effects of COMP-Ang-1 corresponded to increased phosphorylation of Akt and p38 MAPK upon Tie-2 receptor.

Conclusions

COMP-Ang-1 recovers molecular biomarkers of neuropathy, promotes angiogenesis and suppresses inflammation in sciatic nerves of ob/ob mice suggesting COMP-Ang-1 as novel treatment option to improve morphologic and protein expression changes associated with diabetic neuropathy.