Microrheology imaging of fiber suspensions – a case study for lyophilized collagen I in HCl solutions

In fiber suspensions with low optical contrast, the in situ characterization of structural properties with conventional microscopy methods fails. However, overlaying subsequent images of multiple particle tracking (MPT) videos including short trajectories usually discarded in MPT analysis allowed for direct visualization of individual fibers and the network structure of lyophilized collagen I (Coll) distributed in hydrochloric acid solutions. MPT yielded a broad distribution of mean square displacements (MSDs). Freely diffusing tracer particles yielded viscosities indicating that, irrespective of concentration, a constant amount of Coll is dissolved in the aqueous phase. Particles found elastically trapped within fibrous Coll structures exhibited a broad range of time-independent MSDs and we propose a structure comprising multiple fiber bundles with dense regions inaccessible to tracers and elastic regions of different stiffness in between. Bulky aggregates inaccessible to the 0.2 μm tracers exist even at low Coll concentrations, a network of slender fibers evolves above the sol–gel transition and these fibers densify with increasing Coll concentration. This novel MPT-based imaging technique possesses great potential to characterize the fiber distribution in and structural properties of a broad range of biological and technical suspensions showing low contrast when imaged with conventional techniques. Thus, MPT imaging and microrheology will help to better understand the effect of fiber distribution and network structure on the viscoelastic properties of complex suspensions

Towards a description of the degradation of archaeological birch bark

Archaeological birch-bark artefacts from ice patches are rare and little knowledge about their conservation exists. The degradation mechanisms are unknown and it is uncertain how they affect the mechanical properties and the cell structure. Due to this lack of knowledge, the treatments for archaeological birch-bark artefacts usually mimic those for waterlogged wood, which are tuned to the preservation condition of the object. This is assessed by measuring the maximum water content and, in some cases, the basic density and by microscopic examination of microscopic examination. In this paper, it is explored whether these parameters and techniques can be used to characterise the degradation of archaeological birch bark. Light microscopy examinations showed that cell wall deformations and fractures were present in both unaged reference material and archaeological birch bark and are not a distinct attribute of degradation. Cell collapse was not detected in ice-logged samples, while loss of birefringence is a potential tool to characterise degradation. Birch bark cells cannot be saturated with water, not even in the case of waterlogged archaeological samples. The authors conclude that maximum water content is not a diagnostic tool to quantify degradation

Neolithic and Bronze Age archery equipment from alpine ice-patches: A review on components, construction techniques and functionality

The alpine ice-patch sites of Tisenjoch (I), Schnidejoch and Loetschenpass (CH) brought to light the most complete archery equipments known from the European Prehistory. Bows were simple self bows made from yew (Taxus baccata) or elm wood (Ulmus sp.) of different types, but always of man-tall size. The manufacturing process can be described from several finds of unfinished bow blanks, as in the case of the Tisenjoch. Neolithic arrows were made from shoots of hazel (Corylus avellana), guelder rose (Viburnum sp.) or other hardwoods. They were straightened by heat and generally longer and thicker as modern sporting arrows for increased weight and penetration power. Their fletching of three split feathers was practically the same as it is still used today. Bowstrings are extremely rare in European archaeological sites, only two assured samples are known to date, coming from the Tisenjoch and the Schnidejoch ice-patches. They were made from animal sinew fibres which will not be preserved in non-frozen sites. Although there almost certainly was a need for a protective cover of the bow against bad weather, there is only one example of a Neolithic bow case known to date. The cover, made from water resistant birch bark and a little longer as the bow which was carried inside, was found on Schnidejoch. It incorporates a carrying system of leather straps which enabled the user to wear it over the shoulder, keeping the hands free for other tasks. It is supposed that other bow cases which very probably existed in the neolithic, were made from animal hide or leather which would not survive in waterlogged sites. That there were protective carrying devices for archery gear is testified by the leather arrow quiver found on Tisenjoch and by numerous ethnographic and historic examples

EPHB2 germline variants in patients with colorectal cancer or hyperplastic polyposis

BACKGROUND: Ephrin receptor B2 (EPHB2) has recently been proposed as a novel tumor suppressor gene in colorectal cancer (CRC). Inactivation of the gene has been shown to correlate with progression of colorectal tumorigenesis, and somatic mutations have been reported in both colorectal and prostate tumors. METHODS: Here we have analyzed the EPHB2 gene for germline alterations in 101 individuals either with 1) CRC and a personal or family history of prostate cancer (PC), or 2) intestinal hyperplastic polyposis (HPP), a condition associated with malignant degeneration such as serrated adenoma and CRC. RESULTS: Four previously unknown missense alterations were observed, which may be associated with the disease phenotype. Two of the changes, I361V and R568W, were identified in Finnish CRC patients, but not in over 300 Finnish familial CRC or PC patients or more than 200 population-matched healthy controls. The third change, D861N, was observed in a UK HPP patient, but not in additional 40 UK HPP patients or in 200 UK healthy controls. The fourth change R80H, originally identified in a Finnish CRC patient, was also found in 1/106 familial CRC patients and in 9/281 healthy controls and is likely to be a neutral polymorphism. CONCLUSION: We detected novel germline EPHB2 alterations in patients with colorectal tumors. The results suggest a limited role for these EPHB2 variants in colon tumor predisposition. Further studies including functional analyses are needed to confirm this

Microenvironmental regulation of metastasis

Metastasis is a multistage process that requires cancer cells to escape from the primary tumour, survive in the circulation, seed at distant sites and grow. Each of these processes involves rate-limiting steps that are influenced by non-malignant cells of the tumour microenvironment. Many of these cells are derived from the bone marrow, particularly the myeloid lineage, and are recruited by cancer cells to enhance their survival, growth, invasion and dissemination. This Review describes experimental data demonstrating the role of the microenvironment in metastasis, identifies areas for future research and suggests possible new therapeutic avenues

Schnydejoch - Objekte aus Holz und Rinde

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Birch bark – the material and its processing with regard to the examination of the earliest known Neolithic bow case.

During prehistory times birch bark was an easily available resource thanks to the widespread presence of the birch tree in the natural landscape. Due to its perishable nature, archaeological objects made of birch bark like containers, hats, fishing equipment and torches are rare, but they do demonstrate the versatile uses of this material. Birch bark is water-repellent, lightweight, durable and can be worked similar to leather. Between 2003 and 2005 the earliest known protective case for a bow was recovered out of a melting ice patch at the Schnidejoch Pass in the Bernese Alps, Switzerland and represents a new example of the use of birch bark. The so-called bow case is made of differently oriented, superimposed birch bark strips, measures 1.7 m in lengths and is dated between 2880 and 2640 BC. This outstanding object – which lacks comparable parallels - was the focus of an interdisciplinary four years research project aiming to understand the choice of birch bark as construction material and the technology available to Neolithic hunter-gatherers. Fundamental for this was an intensive study of the object itself. Information on the harvesting and processing were gained by reviewing the published literature about indigenous knowledge and by interviewing craftspeople working with birch bark. The presentation/paper will present principal conclusions concerning the material properties, the harvesting process and the use of birch bark. The deep understanding of this material and its processing allows for a better interpretation of the manufacture traces found on the bow case and on other objects made of birch bark

On the rolling and plasticization of birch bark

Freshly harvested outer birch bark is a pliable, leather-like material, but within a short period it loses flexibility and becomes rigid. Further, still during the removal from the tree, it starts to roll back upon itself with the inner side out. This is relevant to conservators as objects made of birch bark do often show this type of deformation and need to be re-shaped. In this paper methods used nowadays by craftspeople to avoid the rolling of the outer birch bark (phellem) and flexibilization methods used by both craftspeople and conservators are reviewed. Some of these methods like the use of solvent vapours have some major drawbacks as birch bark contains a high amount of soluble substances within the cell lumen that can be solubilized during the treatment. In order to optimize treatment procedures for birch bark artefacts in the future it is important to understand the rolling of birch bark. We provide for the first time an explanation of the rolling pattern based on the microscopical analysis of the phellem cell dimensions on 3 to 6 years old twigs of Betula pendula and mature barks. The cell size and number measurements showed that the tangential cell length in the outer phellem layer is larger than in the inner layers while their number is lower. The combination of these two factors lead to the rolling of the bark with the inner side out once the inner tension is released upon the removal from the tree

Towards a description of the degradation of archaeological birch bark

ABSTRACT Archaeological birch-bark artefacts from ice patches are rare and little knowledge about their conservation exists. The degradation mechanisms are unknown and it is uncertain how they affect the mechanical properties and the cell structure. Due to this lack of knowledge, the treatments for archaeological birch-bark artefacts usually mimic those for waterlogged wood, which are tuned to the preservation condition of the object. This is assessed by measuring the maximum water content and, in some cases, the basic density and by microscopic examination of microscopic examination. In this paper, it is explored whether these parameters and techniques can be used to characterise the degradation of archaeological birch bark. Light microscopy examinations showed that cell wall deformations and fractures were present in both unaged reference material and archaeological birch bark and are not a distinct attribute of degradation. Cell collapse was not detected in ice-logged samples, while loss of birefringence is a potential tool to characterise degradation. Birch bark cells cannot be saturated with water, not even in the case of waterlogged archaeological samples. The authors conclude that maximum water content is not a diagnostic tool to quantify degradation