The type III secretion system needle,tip, and translocon

Many Gram‐negative bacteria pathogenic to plants and animals deploy the type III secretion system (T3SS) to inject virulence factors into their hosts. All bacteria that rely on the T3SS to cause infectious diseases in humans have developed antibiotic resistance. The T3SS is an attractive target for developing new antibiotics because it is essential in virulence, and part of its structural component is exposed on the bacterial surface. The structural component of the T3SS is the needle apparatus, which is assembled from over 20 different proteins and consists of a base, an extracellular needle, a tip, and a translocon. This review summarizes the current knowledge on the structure and assembly of the needle, tip, and translocon.     

Middle Triassic conodont apparatus architecture revealed by synchrotron X-ray microtomography

The composition of conodont apparatuses is crucial for understanding the feeding mechanisms of these early vertebrates. However, the multielement apparatus reconstructions of most species remain equivocal because they have been inferred from loose element collections, guided by knowledge from rare articulated ‘bedding plane assemblages’ and fused clusters, often from distantly related taxa. Even these natural assemblages can be difficult to interpret because the component elements can be closely juxtaposed or embedded in matrix, making it hard to discern the morphology of each element and their relative positions within the architecture of the feeding apparatus. Here we report five exceptionally preserved conodont clusters from the Middle Triassic Luoping Biota, Yunnan Province, Southwest China. These materials were scanned using synchrotron radiation X-ray tomographic microscopy (SRXTM), revealing the morphology and positional homology of the component elements in the fused clusters. We confirm that the apparatus of Nicoraella was composed of eight types of elements, comprising a total of 15 elements. SRXTM reveals the positional homologies of the component elements, viz. a single alate element is located in the S₀ position, flanked successively abaxially by pairs of breviform digyrate S₁ and S₂ elements, bipennate S₃ and S₄ elements, and a pair of inwardly curved breviform digyrate M elements. Carminate elements occupy the P₁ and P₂ positions. The apparatus of Nicoraella is among the most completely characterised of all conodonts and serves as a template for the reconstruction of gondollellids.     

Variable actin dynamics requirement for the exit of different cargo from the trans-Golgi network

Efficient post-Golgi trafficking depends on microtubules, but actin filaments and actin-associated proteins are also postulated. Here we examined, by inverse fluorescence recovery after photobleaching, the role of actin dynamics in the exit from the TGN of fluorescent-tagged apical or basolateral and raft or non-raft-associated cargoes. Either the actin-stabilizing jasplakinolide or the actin-depolymerising latrunculin B variably but significantly inhibited post-Golgi traffic of non-raft associated apical p75NTR and basolateral VSV-G cargoes. The TGN-exit of the apical-destined VSV-G mutant was impaired only by latrunculin B. Strikingly, the raft-associated GPI-anchor protein was not affected by either actin toxin. Results indicate that actin dynamics participates in the TGN egress of both apical- and basolateral-targeted proteins but is not needed for apical raft-associated cargo.     

Osteopathy of the pectoral and pelvic limbs including pentadactyly in a young Kestrel (Falco t. tinnunculus)

Summary A five and a half weeks old female Kestrel exhibiting osteopathy of the pectoral and pelvic limbs, including symmetrical hyperdactyly, was investigated in order to clarify the pattern of the involved anatomical alterations and the possible causes of this developmental malformation. In the pectoral limb it consisted of a triplication of the alular digit, in the pelvic limb of a duplication of digit I. The live young Kestrel was observed for a period of two weeks to ascertain that it was unable to fly or procure prey on its own. After its death radiographs were taken and, apart from an eidonomic inspection including the wing claws, a detailed macroscopic dissection of the musculature of the pectoral and pelvic limbs was carried out using the in-water-method. Consecutive dissection steps were documented by a series of photographic slides. The relevant musculature, particularly that of the supernumerary digits, was recorded in proportional drawings. Subsequent to maceration of the limbs the isolated bones were reassembled according to the radiographs and also documented by means of photographs and drawings. This anatomical approach produced a reliable reconstruction of the skeletomuscular apparatus of the hyperdactylous limb parts. The eidonomic inspection revealed that at least young Kestrels may have two (alular and major digit) or even three wing claws per side. The proximal skeletal elements of both pectoral and pelvic limb were more sturdily built than in a typical Kestrel of comparable age. The proximal elements of the pelvic limb, the tarsometatarsus in particular, were shorter than in a typical Kestrel. In addition, the long axis of the tarsometatarsus was laterally bent in the transverse plane so that its proximal articular surfaces were medially inclined. Duplication of the cutaneous and osseous elements in the foot was accompanied by a duplication of some of the muscular and/or tendinous elements supplying digit I proper and the accessory digit I'. There were left-to-right asymmetries of the pedal musculature concerned. In contrast, the two accessory alular digits of each wing were almost completely devoid of musculature. Apart from atypical points of origin or insertion of the remaining distal musculture, left-to-right asymmetries and the two accessory alulae per wing, presumably, affected aerodynamic properties and resulted in flightlessness.A juvenile Kestrel of similar age and without hyperdactyly was dissected for comparison. In addition, the external appearance of the carpometacarpal region of two female Silkies, an obligatory pentadactylous breed of domestic fowl, was inspected and the skeletal parts of their pectoral and pelvic limbs compared with those of the hyperdactylous Kestrel. Our results and a literature review suggest that the symmetrical hyperdactyly in the Kestrel bears striking similarities to the hereditary hyperdactyly observed in certain breeds of domestic fowl. In addition, there is a striking resemblance between the hyperdactyly of the young Kestrel and certain forms of hyperdactyly induced by molecular genetical experiments of other authors on chicks. Comparison with these results taken from the literature suggest that the symmetrical hyperdactyly in the young Kestrel, including the alterations of the proximal skeletal elements, is caused by an unusually early expression of the Hoxd-11 gene group during embryological development. Most likely, this gene group is situated on the 2^nd chromosome in birds just as it is in mammals.

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Osteopathie der Vorder - und Hinterextremitäten, verbunden mit einer symmetrischen Hyperdactylie bei einem jungen Turmfalken (Falco tinnunculus)

Zusammenfassung Ein fünfeinhalb Wochen alter weiblicher Turmfalke mit einer Osteopathie der Vorder- und Hinterextremitäten, verbunden mit einer symmetrischen Hyperdactylie, wurde untersucht, um das Muster der beteiligten anatomischen Veränderungen und die möglichen Ursachen dieser Mißbildung zu erkennen. An der Vorderextremität bestand sie aus einer Verdreifachung des Alula-Fingers, an der Hinterextremität aus einer Verdoppelung der Zehe I. Die Beobachtung des lebenden jungen Turmfalken während eines Zeitraumes von zwei Wochen ergab, dass er flugunfähig war und keine Beute schlagen konnte.Nach seinem Tod und einer Inspektion der Eidonomie, einschließlich der Flügelkrallen, wurden Röntgenaufnahmen angefertigt. Danach folgte eine detaillierte makroskopische Präparation der Flügel- und Beinmuskulatur unter Verwendung der In-Wasser-Methode. Die einzelnen Präparationsschritte wurden anhand von Dia-Serien dokumentiert. Die relevante Muskulatur, insbesondere die der überzähligen Digiti, wurde in proportionsgetreuen Zeichnungen festgehalten. Nach Mazeration der Extremitäten wurden die Einzelknochen, entsprechend den Röntgenbildern, wieder zusammengesetzt und ebenfalls mit Fotografien und Zeichnungen dokumentiert. Dieser anatomische Ansatz lieferte eine zuverlässige Rekonstruktion des Skelett-Muskel-Apparates der hyperdactylen Extremitätenanteile.Die eidonomische Inspektion ergab, dass zumindest junge Turmfalken zwei (Digitus alularis und majoris) oder sogar drei Flügelkrallen haben können. Die proximalen Skelettelemente der Vorder- und Hinterextremität waren deutlich robuster gebaut als bei einem typischen Turmfalken vergleichbaren Alters. Die proximalen Elemente der Hinterextremität, insbesondere der Tarsometatarsus, waren kürzer als bei einem typischen Turmfalken. Darüberhinaus war die Längsachse des Tarsometatarsus in der Transversalebene laterad gekrümmt, so dass sich seine proximalen Gelenkflächen schräg mediad richteten. Entsprechend der kutanen und knöchernen Doppelbildungen des Fußes waren auch einige der Muskeln und Sehnen doppelt vorhanden, welche die eigentliche erste Zehe und die akzessorische erste Zehe versorgten. Es traten Rechts-/Links-Asymmetrien der betreffenden Muskulatur auf. Im Gegensatz dazu waren die beiden akzessorischen Alula-Finger jedes Flügels fast vollständig ohne Muskulatur. Abgesehen von atypischen Ursprungs- und Insertionspunkten der verbleibenden distalen Muskulatur, beeinträchtigten Rechts-/Links-Asymmetrien und die beiden akzessorischen Alulae pro Flügel vermutlich die aerodynamischen Eigenschaften und führten zur Flugunfähigkeit.Ein junger Turmfalke ähnlichen Alters ohne Hyperdactylie wurde zum Vergleich präpariert. Zusätzlich wurde die äußere Erscheinung der Carpometacarpal-Region zweier Seidenhühner, einer obligatorisch pentadactylen Hühnerrasse, inspiziert und die Skelettelemente ihrer Vorder- und Hinterextremitäten mit denen des hyperdactylen Turmfalken verglichen. Unsere Ergebnisse und ein Überblick der Literatur lassen auffallende Übereinstimmungen zwischen der symmetrischen Hyperdactylie des jungen Turmfalken und der erblichen Hyperdactylie bestimmter Hühnerrassen erkennen. Darüberhinaus besteht eine auffallende übereinstimmung zwischen der Hyperdactylie des jungen Turmfalken und bestimmten Formen der Hyperdactylie, welche von anderen Autoren durch molekulargenetische Experimente an Hühnerküken induziert wurden. Ein Vergleich mit diesen Ergebnissen aus der Literatur legt nahe, dass die symmetrische Hyperdactylie des jungen Turmfalken, einschließlich der Veränderungen der proximalen Skelettelemente, durch eine ungewöhnlich frühe Expression der Hoxd-11 Gengruppe im Laufe der Embryonalentwicklung verursacht wurde. Sehr wahrscheinlich ist diese Gengruppe bei Vögeln auf dem zweiten Chromosom lokalisiert — ebenso wie bei Säugetieren.

     

Golgi clusters and vesicles mediate mitotic inheritance independently of the endoplasmic reticulum

We have examined the fate of Golgi membranes during mitotic inheritance in animal cells using four-dimensional fluorescence microscopy, serial section reconstruction of electron micrographs, and peroxidase cytochemistry to track the fate of a Golgi enzyme fused to horseradish peroxidase. All three approaches show that partitioning of Golgi membranes is mediated by Golgi clusters that persist throughout mitosis, together with shed vesicles that are often found associated with spindle microtubules. We have been unable to find evidence that Golgi membranes fuse during the later phases of mitosis with the endoplasmic reticulum (ER) as a strategy for Golgi partitioning (Zaal, K.J., C.L. Smith, R.S. Polishchuk, N. Altan, N.B. Cole, J. Ellenberg, K. Hirschberg, J.F. Presley, T.H. Roberts, E. Siggia, et al. 1999. Cell. 99:589-601) and suggest that these results, in part, are the consequence of slow or abortive folding of GFP-Golgi chimeras in the ER. Furthermore, we show that accurate partitioning is accomplished early in mitosis, by a process of cytoplasmic redistribution of Golgi fragments and vesicles yielding a balance of Golgi membranes on either side of the metaphase plate before cell division.     

Reflective properties of different eyespot types in dinoflagellates

The reflective properties of different types of dinoflagellate eyespots were investigated using confocal laser scanning microscopy in the epireflection contrast mode. Although the eyespots studied differed with respect to localization (cytosol or plastid) and organization of the globule layer(s), all types effectively absorbed and reflected blue-green laser light (principal lines of 488/514 nm). The relative orientation of the eyespot surface towards the light source strongly influenced the reflective properties. Maximal reflection occurred when the eyespot surface was approximately perpendicular to the light source and rapidly decreased at increasing angles of light incidence. Horizontal and vertical optical sectioning of live and fixed cells resolved differences in the reflection patterns. Focusing of reflected light on the basal portion of the longitudinal flagellum was observed for the cytosolic eyespot of Glenodinium sp. and the triple membrane-bounded eyespot of Peridinium foliaceum, presumably a vestige of a host plastid. This flagellum is thought to be mainly involved in mediating orientational movement responses. In contrast, the reflection patterns obtained from the eyespot of Woloszynskia pascheri, which represents the third and most commonly observed dinoflagellate eyespot type within a plastid, point to only minor focusing. Reflection signals could be followed a considerable distance into the sulcus in all cases, indicating that in dinoflagellate eyespots, irrespective of the presumed receptor location (plasma membrane overlying the eyespot and/or the basal part of the longitudinal flagellum), back reflection of non-absorbed light can enhance the excitation probability of the photoreceptor(s). Such a combined reflection/absorption screen allows maximal contrast modulation and will, in conjunction with the specialized geometry of the dinoflagellate eyespots, increase the directionality of these eyespot aparatuses considerably.     

Calcium release from the Golgi apparatus and the endoplasmic reticulum in HeLa cells stably expressing targeted aequorin to these compartments

Extracellular agonists mobilize Ca2+ from SERCA-comprising intracellular Ca2+ stores located in both the Golgi apparatus and the endoplasmic reticulum. Ca2+ release from both these compartments was studied in HeLa cells stably expressing the luminescent Ca2+ indicator aequorin specifically targeted to these compartments. Changes in lumenal [Ca2+] as detected by the aequorin measurements were correlated with parallel changes in total Ca2+ content of the stores. The latencies and initial rates of Ca2+ release from the Golgi apparatus and the endoplasmic reticulum were quite similar. However, maximal Ca2+ release measured with Golgi-targeted aequorin terminated faster than that from the endoplasmic reticulum. The rate and extent of Ca2+ depletion from both compartments correlated well with the peak amplitude of the cytosolic [Ca2+] rise. Time-course experiments further revealed that the peak of the cytosolic Ca2+ response occurred before the lumenal [Ca2+] reached its lowest level. We conclude that both the Golgi apparatus and the endoplasmic reticulum contribute to the rise in cytosolic [Ca2+] upon agonist stimulation, but the kinetics of the Ca2+ release are different.     

Dosimetric analysis of the carousel setup for the exposure of rats at 1.62 GHz

The so-called carousel setup has been widely utilized for testing the hypotheses of adverse health effects on the central nervous system (CNS) due to mobile phone exposures in the frequency bands 800-900 MHz. The objectives of this article were to analyze the suitability of the setup for the upper mobile frequency range, i.e., 1.4-2 GHz, and to conduct a detailed experimental and numerical dosimetry for the setup at the IRIDIUM frequency band of 1.62 GHz. The setup consists of a plastic base on which ten rats, restrained in radially positioned tubes, are exposed to the electromagnetic field emanating from a sleeved dipole antenna at the center. Latest generation miniaturized dosimetric E field and temperature probes were used to measure the specific absorption rate (SAR) inside the brain of three rat cadavers of the Lewis strain and two rat cadavers of the Fisher 344 strain. A numerical analysis was conducted on the basis of three numerical rat phantoms with voxel sizes between 1.5 and 0.125 mm3 that are based on high resolution MRI scans of a 300 g male Wistar rat and a 370 g male Sprague-Dawley rat. The average of the assessed SAR values in the brain was 2.8 mW/g per W antenna input power for adult rats with masses between 220 and 350 g and 5.3 mW/g per W antenna input power for a juvenile rat with a mass of 95 g. The strong increase of the SAR in the brain with decreasing animal size was verified by simulations of the absorption in numerical phantoms scaled to sizes between 100 and 500 g with three different scaling methods. The study also demonstrated that current rat phantom models do not provide sufficient spatial resolution to perform absolute SAR assessment for the brain tissue. The variation of the SAR(brain)(av) due to changes in position was assessed to be in the range from +15% to -30%. A study on the dependence of the performance of the carousel setup on the frequency revealed that efficiency, defined as SAR(brain)(av) per W antenna input power, and the ratio between SAR(brain)(av) and SAR(body)(av) are optimal in the mobile communications frequency range, i.e., 0.8-3 GHz.     

Morphofunctional study of the bill and hyoid apparatus of Momotus momota (Aves, Coraciiformes, Momotidae): implications for omnivorous feeding adaptation in motmots

The present study contrasts available biological data and results of morphofunctional analyses of the bill and hyoid apparatus in motmots. It shows that these omnivorous birds, which take relatively large food items, possess osteomuscular peculiarities that enable them to process these items as a whole in order to soften or cut them, and make them suited for easy ingestion. For that, they use the crenate edges of their rhamphotheca. Their jaws work as a highly mobile saw-like system. Their mutual movements, enhanced by the fact that particular dispositions of the hyoid apparatus rise the tongue and the supported items high up into buccal cavity, facilitate an effective clamping of items that can be moved along the jaws and be quite appropriately processed.