Contribution of postnatal collagen reorientation to depth-dependent mechanical properties of articular cartilage

The collagen fibril network is an important factor for the depth-dependent mechanical behaviour of adult articular cartilage (AC). Recent studies show that collagen orientation is parallel to the articular surface throughout the tissue depth in perinatal animals, and that the collagen orientations transform to a depth-dependent arcade-like structure in adult animals. Current understanding on the mechanobiology of postnatal AC development is incomplete. In the current paper, we investigate the contribution of collagen fibril orientation changes to the depth-dependent mechanical properties of AC. We use a composition-based finite element model to simulate in a 1-D confined compression geometry the effects of ten different collagen orientation patterns that were measured in developing sheep. In initial postnatal life, AC is mostly subject to growth and we observe only small changes in depth-dependent mechanical behaviour. Functional adaptation of depth-dependent mechanical behaviour of AC takes place in the second half of life before puberty. Changes in fibril orientation alone increase cartilage stiffness during development through the modulation of swelling strains and osmotic pressures. Changes in stiffness are most pronounced for small stresses and for cartilage adjacent to the bone. We hypothesize that postnatal changes in collagen fibril orientation induce mechanical effects that in turn promote these changes. We further hypothesize that a part of the depth-dependent postnatal increase in collagen content in literature is initiated by the depth-dependent postnatal increase in fibril strain due to collagen fibril reorientatio

Optimum prey capture techniques in fish

In this thesis hydrodynamic principles are used to quantify relations between form and function in the prey capture mechanism of actinopterygian fish. This work is closely related to the papers on the hydrodynamics of fish feeding by Muller et al. (1982) and Muller & Osse (in press). The effectiveness of different head forms and movements for prey uptake (in various habitats) is investigated by model simulations and verified by flow visualization and pressure measurements.Chapter 1 presents a technique to visualize the flow in 3-D around the mouth of the fish, sucking its prey. An expanding and compressing cylindrical or conical model of the fish's mouth cavity is used to quantify the relation between head movements and swimming. The opercular and branchiostegal valves are shown to function as control devices to obtain an optimal flow rate through the mouth aperture. The theoretical predictions were verified experimentally for the rainbow trout ( Salmo gairdneri ). Likewise, data from the literature appeared to agree with these hypotheses.Chapter 2 quantifies the contributions of the forward movement of the fish, the expansion of the mouth cavity and a possible protrusion of the jaws to the velocity of the prey. Optimum sucking techniques (i.e. techniques maximizing the chance of prey capture) in relation to swimming speed and habitat properties are derived by model simulations. Maximization of the initial prey distance by an exact adjustment of mouth expansion is rather useless for a fish. Much more is gained if the fish abducts its opercula at the maximal rate when the prey enters the mouth.Chapter 3 discusses recording techniques for pressures in prey-sucking fish. The dynamic properties of different measurement systems are investigated by Fourier analysis. Also, the frequency content of records of the fluctuating pressure inside the fish's mouth during feeding is shown. Prey capture events of different fish species are simulated using the hydrodynamical model of Muller et al. (1982). Measured and simulated pressure curves are compared and the effects of the use of different boundary conditions in the model are discussed. The literature on pressure measurements in prey-sucking fish is reviewed

Aspects of syringeal mechanics in avian phonation

The vocal organ of birds, the syrinx, is formed by modified cartilages of the trachea and bronchi. Recently, the use of thin, flexible endoscopes has made direct observation of the syrinx possible in situ. The effects of direct muscle stimulation on the syringeal aperture identified adductor and abductor muscles, confirming results from electromyographic studies. Endoscopic observations also revealed the dynamics of syringeal reconfiguration during phonation. In songbirds, phonation is initiated by rostrad movement and stretching of the syrinx together with simultaneous movement of the medial and lateral labia into the bronchial lumen where they form a narrow slot. The medial tympaniform membranes play a minor role in vocalization as their removal causes only small changes to song. In the tracheal syrinx of the pigeon, sound production is initiated by almost full adduction of the lateral tympaniform membranes into the tracheal lumen, where they bulge rostrally during phonation. Endoscopic observation combined with vibration detection by laser light suggests that the avian sound generating mechanism is a pulse-tone mechanism similar to that in the human larynx, with the labia (or lateral tympaniform membranes) forming a pneumatic valve. A numerical, two-dimensional model of the pigeon syrinx is propose

Zuurstofopname in de vroege ontwikkeling van vissen

In een pas bevrucht vissenei is nog geen stelsel van bloedvaten aanwezig. Toch heeft de embryo zuurstof en andere voedingsstoffen nodig. De dooier blijkt een belangrijke rol te vervullen bij de opname van zuursto

Synchronous and metachronous urothelial carcinoma of the upper urinary tract and the bladder: Are they clonally related? A systematic review

Purpose: Following radical nephroureterectomy for upper urinary tract urothelial carcinoma (UTUC), intravesical recurrence (IVR) is found in 22% to 47% of patients. Patients with a primary urothelial carcinoma of the bladder (UCB) have an increased risk of a future UTUC (1%–5%). Paired UTUC and UCB might represent clonally related tumors due to intraluminal seeding of tumor cells or might be separate entities of urothelial carcinoma caused by field cancerization. We systematically reviewed all the relevant literature to address the possible clonal relation of UTUC and paired UCB. Materials and Methods: MEDLINE, EMBASE, and COCHRANE databases were systematically searched for relevant citations published between January 2000 and July 2019. This study was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Of 5038 citations identified, 86 full papers were screened, and 9 studies met the inclusion criteria. Results: The populations studied and the molecular techniques used to assess clonality of UTUC and paired UCB differed largely over time. Eight studies reported on primary UTUC and meta- or synchronous IVR without a history of UCB. A total of 118 tumors

Antagonistic effects of transforming growth factor-beta on vitamin D3 enhancement of osteocalcin and osteopontin transcription: reduced interactions of vitamin D receptor/retinoid X receptor complexes with vitamin E response elements

Osteocalcin and osteopontin are noncollagenous proteins secreted by osteoblasts and regulated by a complex interplay of systemic and locally produced factors, including growth factors and steroid hormones. We investigated the mechanism by which transforming growth factor-beta (TGF beta) inhibits 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3)-enhanced expression of the osteocalcin (OC) and osteopontin (OP) genes. ROS 17/2.8 cells, in which both genes are expressed, were transfected with reporter constructs driven by native (i.e. wild-type) rat OC and mouse OP promoters. TGF beta abrogated the 1,25-(OH)2D3 enhanced transcription of both the OC and OP genes. The inhibitory TGF beta response for each requires vitamin D response element (VDRE) sequences, although there are additional contributions from proximal basal regulatory elements. These transcriptional effects were further investigated for contribution of the trans-activating factors, which interact with OC and OP VDREs, involving the vitamin D receptor (VDR) and retinoid X receptor (RXR). Gel mobility shift assays show that TGF beta significantly reduces induction of the heterodimers VDR/RXR complexes in 1,25-(OH)2D3-treated ROS 17/2.8 cells. However, Western blot and ligand binding analysis reveal that TGF beta does not affect nuclear availability of the VDR. We also show that activator protein-1 activity is up-regulated by TGF beta; thus, activator protein-1 binding sites in the OC promoter may potentially contribute to inhibitory effects of TGF beta on basal transcription. Our studies demonstrate that the inhibitory action of TGF beta on the 1,25-(OH)2D3 enhancement of OC and OP transcription in osteoblastic cells results from modulations of protein-DNA interactions at the OC and OP VDRE, which cannot be accounted for by changes in VDR protein levels. As OC and OP participate in bone turnover, our results provide insight into the contributions of TGF beta and 1,25-(OH)2D3 to VDR-mediated gene regulatory mechanism operative in bone formation and/or resorption events

Quantifying heterogeneous responses of fish community size structure using novel combined statistical techniques

To understand changes in ecosystems, the appropriate scale at which to study them must be determined. Large marine ecosystems (LMEs) cover thousands of square kilometres and are a useful classification scheme for ecosystem monitoring and assessment. However, averaging across LMEs may obscure intricate dynamics within. The purpose of this study is to mathematically determine local and regional patterns of ecological change within an LME using empirical orthogonal functions (EOFs). After using EOFs to define regions with distinct patterns of change, a statistical model originating from control theory is applied (Nonlinear AutoRegressive Moving Average with eXogenous input – NARMAX) to assess potential drivers of change within these regions. We have selected spatial data sets (0.5° latitude × 1°longitude) of fish abundance from North Sea fisheries research surveys (spanning 1980–2008) as well as of temperature, oxygen, net primary production and a fishing pressure proxy, to which we apply the EOF and NARMAX methods. Two regions showed significant changes since 1980: the central North Sea displayed a decrease in community size structure which the NARMAX model suggested was linked to changes in fishing; and the Norwegian trench region displayed an increase in community size structure which, as indicated by NARMAX results, was primarily linked to changes in sea-bottom temperature. These regions were compared to an area of no change along the eastern Scottish coast where the model determined the community size structure was most strongly associated to net primary production. This study highlights the multifaceted effects of environmental change and fishing pressures in different regions of the North Sea. Furthermore, by highlighting this spatial heterogeneity in community size structure change, important local spatial dynamics are often overlooked when the North Sea is considered as a broad-scale, homogeneous ecosystem (as normally is the case within the political Marine Strategy Framework Directive)