Development and physiology of follicular atresia during ovarian growth in the house fly, Musca domestica

Atretic follicles regularly occur in the ovary of the house fly, Musca domestica. The frequency of ovarian follicular atresia and the proportion of atretic follicles per ovary are related to the stage of oögenesis and to the age of the females. Only vitellogenic follicles may become atretic. The atresia may occur at any stage of vitellogenesis, though most follicles become atretic in mid-vitellogenesis. Atretic follicles are completely resorbed within 24–36 hr. The follicle cells may play a synthesizing role during growth and disintegrating one during follicle resorption. The induction of glycogen synthesis by the cessation of RNA and protein synthesis and by vitellogenesis in normal follicles is discussed. The same processes occur prematurely in the atretic follicle which can be thus distinguished by a high content of glycogen.     

Can we measure ecological sustainability? Landscape pattern as an indicator for naturalness and land use intensity at regional,national and European level

European landscapes have been shaped over the centuries by processes related to human land use, which are reflected in regionally distinct landscape patterns. Since landscape pattern has been linked to biodiversity and other ecological values of the landscapes, this paper explores landscape pattern as a tool for ecological sustainability assessments at the regional (Austrian Cultural Landscapes), national (Austria) and European (European Union + Norway, Switzerland) level with focus on agricultural landscapes. A set of landscape metrics served as a basis to assess naturalness and geometrisation of Austrian and European landscapes as a proxy for their sustainability. To achieve an accurate spatially explicit assessment, we applied a spatial reference framework consisting in units that are homogeneous in biophysical and socio-economic contexts, adapted the regional approach for its application at European level, and developed relative sustainability thresholds for the landscape metrics. The analyses revealed that several landscape metrics, particularly the “Number of Shape Characterising Points” showed a high correlation with the degree of naturalness. The sustainability map of Austria based on an ordinal regression model revealed well-known problem regions of ecological sustainability. At the European level, the relative deviation from the average pattern showed clearly the simplification processes in the landscapes. However, a better spatial resolution of land cover data would add to the refinement of pattern analysis in regions and therefore the assessment of sustainability. We recommend the combination of information of different scales for the formulation and implementation of sustainability policies.     

Temperaturadaptation der Sauerstoffbindung des Blutes von Rana esculenta L.

Zusammenfassung Bei einer raschen Temperatursteigerung wird die Leistungsfähigkeit des Blutes hinsichtlich der Sauerstoffaufladung durch eine Rechtsverschiebung der Dissotiationskurve herabgesetzt. Rana esculenta besitzt 2 Regulationen, um diesen Effekt zum Teil zu kompensieren. Überführt man kalt-angepaßte Tiere in mittlere Temperaturen und beläßt sie in diesen, so steigert sich durch einen langsam einsetzenden Anpassungsvorgang der Hämoglobingehalt des Blutes. Nach Umsetzen der Frösche in noch höhere Temperaturen wird durch einen weiteren Regulationsvorgang die Sauerstoffaffinität, d. h. der Sauerstoffgehalt, bezogen auf gleiche Hämoglobinmengen, gesteigert, wodurch die Rechtsverschiebung der Dissoziationskurve teilweise wieder rückgängig gemacht wird. Beide Regulationen sind reversibel.Dissertation bei der Philosophischen Fakultät der Universität Kiel, Teil II (Anregung und Anleitung: Prof. Dr. H. Precht). Die photometrischen Messungen wurden mit einem Pulfrich-Photometer ausgeführt, welches die Deutsche Forschungsgemeinschaft Herrn Prof. Precht zur Verfügung stellte.     

Nitrogenase activity in composting horse bedding and leaves

To date little or no nitrogen fixation has been found in composting materials. However, some materials have high C:N ratios and thus might be expected to support nitrogen fixation. We examined windrows of composting horse bedding and leaves for nitrogenase activity via acetylene reduction and used carbon monoxide controls to differentiate ethylene evolved by nitrogenase from that evolved by endogenous processes. In both piles temperatures were substantially elevated and partial pressures of oxygen greatly reduced thus indicating vigorous microbial activity. In the horse bedding, there were only low rates of ethylene evolution and little of this was due to nitrogen fixation. In contrast, much higher rates of ethylene evolution were measured in the leaf pile and 94% of this was due to nitrogenase activity. We estimate that the leaf pile fixed approximately 0.062 mg N/g leaves during a 5-week period.     

Professor Dr. Geoffrey Burnstock (1929–2020)

Purinergic Signalling -     

Arguments against the significance of the Fenton reaction contributing to signal pathways under in vivo conditions

One of the common explanations for oxidative stress in the physiological milieu is based on the Fenton reaction, i.e. the assumption that radical chain reactions are initiated by metal-catalyzed electron transfer to hydrogen peroxide yielding hydroxyl radicals. On the other hand — especially in the context of so-called “iron switches” — it is postulated that cellular signaling pathways originate from the interaction of reduced iron with hydrogen peroxide.

Using fluorescence detection and EPR for identification of radical intermediates, we determined the rate of iron complexation by physiological buffer together with the reaction rate of concomitant hydroxylations of aromatic compounds under aerobic and anaerobic conditions. With the obtained overall reaction rate of 1,700 M^-1s^-1 for the buffer-dependent reactions and the known rates for Fenton reactions, we derive estimates for the relative reaction probabilities of both processes.

As a consequence we suggest that under in vivo conditions initiation of chain reactions by hydroxyl radicals generated by the Fenton reaction is of minor importance and hence metal-dependent oxidative stress must be rather independent of the so-called “peroxide tone”. Furthermore, it is proposed that — in the low (subtoxic) concentration range — hydroxylated compounds derived from reactions of “non-free” (crypto) OH radicals are better candidates for iron-dependent sensing of redox-states and for explaining the origin of cellular signals than the generation of “free” hydroxyl radicals.     

Antibodies to Heteromeric Glycolipid Complexes in Guillain-Barré Syndrome

Autoantibodies are infrequently detected in the sera of patients with the demyelinating form of Guillain-Barré syndrome most commonly encountered in the Western world, despite abundant circumstantial evidence suggesting their existence. We hypothesised that antibody specificities reliant on the cis interactions of neighbouring membrane glycolipids could explain this discrepancy, and would not have been detected by traditional serological assays using highly purified preparations of single gangliosides. To assess the frequency of glycolipid complex antibodies in a Western European cohort of patients GBS we used a newly developed combinatorial glycoarray methodology to screen against large range of antigens (11 gangliosides, 8 other single glycolipids and 162 heterodimeric glycolipid complexes). Serum samples of 181 patients from a geographically defined, Western European cohort of GBS cases were analysed, along with 161 control sera. Serum IgG binding to single gangliosides was observed in 80.0% of axonal GBS cases, but in only 11.8% of cases with demyelinating electrophysiology. The inclusion of glycolipid complexes increased the positivity rate in demyelinating disease to 62.4%. There were 40 antigens with statistically significantly increased binding intensities in GBS as compared to healthy control sera. Of these, 7 complex antigens and 1 single ganglioside also produced statistically significantly increased binding intensities in GBS versus neurological disease controls. The detection of antibodies against specific complexes was associated with particular clinical features including disease severity, requirement for mechanical ventilation, and axonal electrophysiology. This study demonstrates that while antibodies against single gangliosides are often found in cases with axonal-type electrophysiology, antibodies against glycolipid complexes predominate in cases with demyelinating electrophysiology, providing a more robust serum biomarker than has ever been previously available for such cases. This work confirms the activation of the humoral immune system in the dysimmune disease process in GBS, and correlates patterns of antigen recognition with different clinical features.     

The platelet P2Y12 receptor under normal and pathological conditions. Assessment with the radiolabeled selective antagonist [3H]PSB-0413

Various radioligands have been used to characterize and quantify the platelet P2Y₁₂ receptor, which share several weaknesses: (a) they are metabolically unstable and substrates for ectoenzymes, (b) they are agonists, and (c) they do not discriminate between P2Y₁ and P2Y₁₂. We used the [³H]PSB-0413 selective P2Y₁₂ receptor antagonist radioligand to reevaluate the number of P2Y₁₂ receptors in intact platelets and in membrane preparations. Studies in humans showed that: (1) [³H]PSB-0413 bound to 425 ± 50 sites/platelet (K_D = 3.3 ± 0.6 nM), (2) 0.5 ± 0.2 pmol [³H]PSB-0413 bound to 1 mg protein of platelet membranes (K_D = 6.5 ± 3.6 nM), and (3) competition studies confirmed the known features of P2Y₁₂, with the expected rank order of potency: AR-C69931MX > 2MeSADP ≫ ADPβS > ADP, while the P2Y₁ ligand MRS2179 and the P2X₁ ligand α,β-Met-ATP did not displace [³H]PSB-0413 binding. Patients with severe P2Y₁₂ deficiency displayed virtually no binding of [³H]PSB-0413 to intact platelets, while a patient with a dysfunctional P2Y₁₂ receptor had normal binding. Studies in mice showed that: (1) [³H]PSB-0413 bound to 634 ± 87 sites/platelet (K_D = 14 ± 4.5 nM) and (2) 0.7 pmol ± 0.3 [³H]PSB-0413 bound to 1 mg protein of platelet membranes (K_D = 9.1 ± 5.3 nM). Clopidogrel and other thiol reagents like pCMBS or DTT abolished the binding both to intact platelets and membrane preparations. Therefore, [³H]PSB-0413 is an accurate and selective tool for radioligand binding studies aimed at quantifying P2Y₁₂ receptors, to identify patients with P2Y₁₂ deficiencies or quantify the effect of P2Y₁₂ targeting drugs.