Models of the geometry of the human ankle bone pulley: two series of geometric models for demonstrating the biomechanics of the ankle joint

2 series of models demonstrate the geometrical shape of the human trochlea tali. We have changed step by step the shape of the 2 flanking articular facets of the trochlea, the course of the edges of the trochlea, and the length of their radii, and so we have found a model responding to the biomechanic conditions of the trochlea tali. The convex surface of this model (corresponding to the superior articular surface, i.e. the facies superior trochleae tali) is a torse, the medial flanking facet (corresponding to the medial articular facet of the trochlea, i.e. the facies malleolaris medialis) is a flat cone, the lateral flanking facet (corresponding to the lateral articular facet of the trochlea, i.e. the facies malleolaris lateralis) is a screwed (helicoidal) face. The resulting model shows the 2 completely different phases of motion in the ankle joint: During dorsiflexion (motion setting out from the neutral position towards the final position of dorsiflexion), the internal malleolus leads the talus, whereas the external malleolus is pushed outwards by the screwed lateral articular facet of the trocheal. The trochlea is moved like a hinge. In the final position of dorsiflexion, the malleoli tightly embrace the 2 flanking facets of the trochlea, whilst an obvious cleft appears dorsally and medially between the superior articular surface of the trochlea and the tibial roof (i.e. the facies articularis inferior tibiae). During plantarflexion (motion setting out from the neutral position towards the final position of plantarflexion), the external malleolus leads the talus, whereas the medial articular facet of the trochlea withdraws from the internal malleolus. The trochlea is moved like a screw. In the final position of plantarflexion, the superior articular surface of the trochlea closely contacts the tibial roof, whilst an obvious cleft appears between the medial articular facet of the trochlea and the internal malleolus.     

Elicitation of volatile compounds in photomixotrophic cell culture of Petroselinum crispum

Photomixotrophic cells of Petroselinum crispum accumulated >500 mg chlorophyll per kg wet weight and grew well in a broad range of phytoeffector conditions. Autoclaved fungal cells were lethal for photoheterotrophic cells, but induced in photomixotrophic cells the formation of volatile n-alkanes, phthalides, coumarins, and elemicine. Most of the compounds elicited reached a concentration maximum between 20 and 30 h after addition of the mycelium, whereas the group of n-alkanes increased steadily during the 90 h monitored. Maximum concentrations were: 12 mg of graveolone, 1 mg of bergapten, 0.5 mg of sedanenolide, and 0.5 mg of n-tetradecane per 1 nutrient medium. A dose/effect relationship was found; 10 to 25 g of fungal wet weight per 1 culture medium resulted in maximum accumulation of volatiles. The formation of volatiles by photomixotrophic in vitro cells is discussed as an integral part of plant responses to ecological stress.     

F?nge von Habichten (Accipiter gentilis) im Wurzacher Ried: Kritische Fragen zu einem beh?rdlich genehmigten Wiedereinbürgerungsprojekt

Zusammenfassung Während des unter der Trägerschaft des Landesjagdverbandes Baden-Württemberg e. V. seit 1978 laufenden Projektes zur Wiedereinbürgerung des Birkhuhnes im Wurzacher Ried wurde behördlicherseits der Wegfang von Habichten unter bestimmten Auflagen genehmigt. Nach Beringung mußten die Vögel wieder freigelassen werden. Eine vergleichende Untersuchung der von den Projektbetreibern veröffentlichten Berichte und der Beringungsdokumente ergab erhebliche Ungereimtheiten. Die aus den Berichten der Projektbetreiber zu entnehmende Zahl von 168 gefangenen, angeblich beringten und angeblich wieder freigelassenen Habichten steht der Zahl von 98 in den Beringungslisten dokumentierten Vögel gegenüber. Bereits ein Vergleich zwischen der Wiederfundrate der dokumentierten Vögel (1 %) mit der Fänglingfundrate der Vogelwarte Radolfzell (13 %) ergab einen hochsignifikanten Unterschied. Auch der Vergleich mit der Fundrate (15 %) einer anderen, parallel laufenden Verfrachtungsstudie zeigte, daß die Wiederfundrate der Wurzacher Habichte hochsignifikant geringer ist. Die Darstellung der Projektbetreiber, wonach 1978–1981 insgesamt 90 Habichte durch die Landesanstalt für Umweltschutz verfrachtet worden sein sollen, wurde durch die Landesanstalt nicht bestätigt. Die Landesanstalt bestätigte nur fünf verfrachtete Habichte aus dem Wurzacher Projekt. Obwohl der Habichtfang im März nicht erlaubt war, haben die Projektbetreiber insgesamt vier Habichte im März gefangen und zumindest einen (nach eigenen Angaben jedoch alle!) auch noch verfrachtet. Vermutlich im Auftrag von Geflügelzüchtern wurden sieben Habichte, darunter vier Altvögel, innerhalb eines kleinen Gebietes in einer Entfernung von 13–18,5 km vom Wurzacher Ried gefangen. So besteht begründeter Verdacht, daß ein beträchtlicher Teil der im oder um das Wurzacher Ried gefangenen Habichte nicht wieder freigelassen, sondern getötet wurde. Eine Reihe der in den Projektberichten enthaltenen Angaben lassen zudem ganz erhebliche Zweifel an der Fachkompetenz der Projektbetreiber aufkommen.

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Goshawk (Accipiter gentilis) trapping in the nature reserve Wurzacher Ried: critical questions on a Black Grouse (Tetrao tetrix) reintroduction project

Summary A Black Grouse reintroduction project was established in 1978 in the nature reserve Wurzacher Ried in southwestern Germany. Since the beginning of this project the staff had a licence to catch, ring and to release but not to kill goshawks. A comparison of the very low Euring-recovery-rate of 1 percent from this project with the Euring-recovery-rate of the Vogelwarte Radolfzell (13 %) showed a significant difference (p=0.00017). In contrast, we found no difference between the recovery-rate (15 %) of a study with almost similar design conducted by the University of Tübingen (Schmidt-Koenig 1982) only 100 km apart from the Wurzacher Ried and the Euring-recovery-rate of the Vogelwarte Radolfzell (p=0.624). The recovery-rate of the reintroduction project differed, however, significantly from the recovery-rate ofSchmidt-Koenig (p=0.006). Furthermore, we found serious inconsistencies between the project reports and the ringing documents concerning this project. Our results indicate, that most of the goshawks caught in the project Wurzacher Ried may not have been released but illegally killed by the project staff.

     

Glycosylinositol-phosphoceramide in the free-living protozoan Paramecium primaurelia: modification of core glycans by mannosyl phosphate.

Glycolipids synthesized in a cell-free system prepared from the free-living protozoan Paramecium primaurelia and labelled with [3H]mannose and [3H]glucosamine using GDP-[3H]mannose and UDP-[3H]N-acetyl glucosamine, respectively, were identified and structurally characterized as glycosylinositol-phosphoceramides (GIP-ceramides). The ceramide-based lipid was also found in the GIP membrane anchor of the G surface antigen of P.primaurelia, strain 156. Using a combination of in vitro labelling with GDP-[3H]mannose and in vivo labelling with 33P, we found that the core glycans of the P.primaurelia GIP-ceramides were substituted with an acid-labile modification identified as mannosyl phosphate. The modification of the glycosylinositol-phospholipid core glycan by mannosyl phosphate has not been described to date in other organisms. The biosynthesis of GIP-ceramide intermediates in P.primaurelia was studied by a pulse-chase analysis. Their structural characterization is reported. We propose the following structure for the putative GIP-ceramide membrane anchor precursor of P.primaurelia surface proteins: ethanolamine phosphate-6Man-alpha 1-2Man-alpha 1-6Man-(mannosyl phosphate)-alpha 1-4glucosamine-inositol-phosphoceramide.     

Rate-controlling steps of oxidative phosphorylation in rat liver mitochondria. A synoptic approach of model and experiment

The contribution of different steps to the control of oxidative phosphorylation in isolated rat liver mitochondria was investigated by a combination of experiments and computer simulations. The parameters of the mathematical model of phosphorylating mitochondria were derived from experimental data. The model correctly describes the competition between ATP utilization inside and outside mitochondria for the ATP generated in mitochondria. On the basis of the good agreement between experiments and simulations, the contribution of different steps to the control of respiration was estimated by computing their control strengths, i.e., the influence of their activities on the rate of respiration. The rate-controlling influences vary depending on the load of oxidative phosphorylation. The predominant steps are: in the fully active state (State 3) — the hydrogen supply to the respiratory chain; in the resting state (State 4) — the proton leak of the mitochondrial inner membrane; in states of non-maximum ATP export — the adenine nucleotide translocator. Titrations of respiration with phenylsuccinate, antimycin, oligomycin and carboxyatractyloside completely support these conclusions.     

A novel circulating tamiami mammarenavirus shows potential for zoonotic spillover

A detailed understanding of the mechanisms underlying the capacity of a virus to break the species barrier is crucial for pathogen surveillance and control. New World (NW) mammarenaviruses constitute a diverse group of rodent-borne pathogens that includes several causative agents of severe viral hemorrhagic fever in humans. The ability of the NW mammarenaviral attachment glycoprotein (GP) to utilize human transferrin receptor 1 (hTfR1) as a primary entry receptor plays a key role in dictating zoonotic potential. The recent isolation of Tacaribe and lymphocytic choriominingitis mammarenaviruses from host-seeking ticks provided evidence for the presence of mammarenaviruses in arthropods, which are established vectors for numerous other viral pathogens. Here, using next generation sequencing to search for other mammarenaviruses in ticks, we identified a novel replication-competent strain of the NW mammarenavirus Tamiami (TAMV-FL), which we found capable of utilizing hTfR1 to enter mammalian cells. During isolation through serial passaging in mammalian immunocompetent cells, the quasispecies of TAMV-FL acquired and enriched mutations leading to the amino acid changes N151K and D156N, within GP. Cell entry studies revealed that both substitutions, N151K and D156N, increased dependence of the virus on hTfR1 and binding to heparan sulfate proteoglycans. Moreover, we show that the substituted residues likely map to the sterically constrained trimeric axis of GP, and facilitate viral fusion at a lower pH, resulting in viral egress from later endosomal compartments. In summary, we identify and characterize a naturally occurring TAMV strain (TAMV-FL) within ticks that is able to utilize hTfR1. The TAMV-FL significantly diverged from previous TAMV isolates, demonstrating that TAMV quasispecies exhibit striking genetic plasticity that may facilitate zoonotic spillover and rapid adaptation to new hosts.     

Cholesterol sensing by CD81 is important for hepatitis C virus entry

CD81 plays a central role in a variety of physiological and pathological processes. Recent structural analysis of CD81 indicates that it contains an intramembrane cholesterol-binding pocket and that interaction with cholesterol may regulate a conformational switch in the large extracellular domain of CD81. Therefore, CD81 possesses a potential cholesterol-sensing mechanism; however, its relevance for protein function is thus far unknown. In this study we investigate CD81 cholesterol sensing in the context of its activity as a receptor for hepatitis C virus (HCV). Structure-led mutagenesis of the cholesterol-binding pocket reduced CD81–cholesterol association but had disparate effects on HCV entry, both reducing and enhancing CD81 receptor activity. We reasoned that this could be explained by alterations in the consequences of cholesterol binding. To investigate this further we performed molecular dynamic simulations of CD81 with and without cholesterol; this identified a potential allosteric mechanism by which cholesterol binding regulates the conformation of CD81. To test this, we designed further mutations to force CD81 into either the open (cholesterol-unbound) or closed (cholesterol-bound) conformation. The open mutant of CD81 exhibited reduced HCV receptor activity, whereas the closed mutant enhanced activity. These data are consistent with cholesterol sensing switching CD81 between a receptor active and inactive state. CD81 interactome analysis also suggests that conformational switching may modulate the assembly of CD81–partner protein networks. This work furthers our understanding of the molecular mechanism of CD81 cholesterol sensing, how this relates to HCV entry, and CD81''s function as a molecular scaffold; these insights are relevant to CD81''s varied roles in both health and disease.