The Myosin Myocardial Mesh Interpreted as a Biological Analogous of Nematic Chiral Liquid Crystals

There are still grey areas in the understanding of the myoarchitecture of the ventricular mass. This is despite the progress of investigation methods since the beginning of the 21st century (diffusion tensor magnetic resonance imaging, microcomputed tomography, and polarised light imaging). The objective of this article is to highlight the specificities and the limitations of polarised light imaging (PLI) of the unstained myocardium embedded in methyl methacrylate (MMA). Thus, to better differentiate our method from other PLI modes, we will refer to it by the acronym PLI-MMA. PLI-MMA shows that the myosin mesh of the compact left ventricular wall behaves like a biological analogous of a nematic chiral liquid crystal. Results obtained by PLI-MMA are: the main direction of the myosin molecules contained in an imaged voxel, the crystal liquid director n, and a regional isotropy index RI that is an orientation tensor, the equivalent of the crystal liquid order parameter. The vector n is collinear with the first eigenvector of diffusion tensor imaging (DTI-MRI). The RI has not been confounded with the diffusion tensor of DTI that gives information about the three eigenvectors of the ellipsoid of diffusion. PLI-MMA gives no information about the collagen network. The physics of soft matter has allowed the revisiting of Streeter’s conjecture on the myoarchitecture of the compact left ventricular wall: “geodesics on a nested set of toroidal surfaces”. Once the torus topology is understood, this characterisation of the myoarchitecture is more accurate and parsimonious than former descriptions. Finally, this article aims to be an enthusiastic invitation to a transdisciplinary approach between physicists of liquid crystals, anatomists, and specialists of imaging.

Description and ontogeny of a 40-million-year-old parasitic isopodan crustacean: Parvucymoides dvorakorum gen. et sp. nov.

A collection of exceptionally well-preserved fossil specimens of crustaceans, clearly representatives of Isopoda, is presented here. Excavated from the late Eocene (approximately 40 million years ago) freshwater sediments of the Trupelník hill field site near Kučlín, Czech Republic, these specimens are preserved with many details of the appendages. The morphological characteristics of the fossils were documented using macro-photography with polarised light, as well as stereo imaging. These characteristics, especially including the trunk appendage morphology, were compared to those of related extant groups from different ontogenetic stages. All specimens are conspecific, representing a single species Parvucymoides dvorakorum gen. et sp. nov. Morphometric analysis of body shapes and sizes of the reconstructed fossils and related extant species were performed. These analyses provided insight into the ontogenetic stages of each reconstructed fossil specimen. In combination with the morphological assessment, the results indicate that the fossils represent at least two (possibly three) developmental stages, including immatures. The morphology of the appendages suggests that these fossils were parasites. The fossils are interpreted as either representatives of Cymothoidae or at least closely related to this group.

PETROGRAPHIC FEATURES AND MODELLING OF SOME WATERFALL ROCKS IN KENYIR LAKE, TERENGGANU: A MICROSCOPIC PERSPECTIVE APPROACH IN SUSTAINABLE GEOTOURISM

Waterfalls around Kenyir Lake, Terengganu naturally serve as an iconic symbol of amazing rock bounded formation amidst the wilderness, which stores a hidden story for millions of years. The waterfalls feeding the Kenyir Lake have become tourists’ main attractions since they are located separately on a different island. There are three naturally picturesque waterfalls worth seeing in the study area, namely Sungai Buweh Waterfall, Lasir Waterfall, and Saok Waterfall, which are made up of granitic rock body that emerged in the Eastern Belt during the Late Triassic (~251.2 Ma). To date, the waterfall landscape in any area concerned with geotourism focusses more on outcrop architecture and geomorphological features, but has only limited accessibility to rock records. This study was carried out to evaluate the geo heritage features, of the waterfall landscape as well as its rock-forming minerals. Three rock samples were carefully collected from the waterfalls and subsequently prepared for optical thin section petrography analysis using a polarised light microscope. The optical thin section petrography further revealed precise mineral compositions, fabrics, and microstructures. A photomicrograph of the thin sections was also taken at low and high magnification levels in plane polarised light (PPL) and cross polarised light (XPL). Additionally, petrographic modelling was constructed using optical microscopic data to help identify a microscopic mineral (a hidden material in rock) in detail so that the mineral becomes clear to both geologists and the public at large. Generally, this modelling will enlighten the public on the material embedded in the rocks and illustrate the importance of learning about rock-forming minerals as well as to embed the idea of making the waterfall a Sustainable Development Goal (SDG). Besides making geology an interesting field to embark on, this mineral find affirms the beauty of the waterfalls for tourism purposes, thereby connecting geotourism and nature. The minerals from various constituents are also useful for scientific heritage purposes and may benefit the economy by serving as sustainable tourism while being part of a geopark.

Investigation of the Kerr effect on polarised light

A constructed Kerr cell with brass electrodes and liquid nitrobenzene was used for studying the Kerr effect on polarised light. Laser light was plane polarised and passed through an energised Kerr cell. The plane polarised light after travelling a path length equal to the cell electrode length in a birefringent medium, suffered optical retardance before passing through an analyser which then transmitted light of certain intensity to a photodiode. Data used were generated from experiments and theoretical considerations using Kerr’s law and Malus’ law. With crossed Polaroids, the Kerr cell behaved as an electro-optic shutter and the maximum light intensity transmitted rose steadily with increased phase difference to about 0.82. With parallel Polaroids, the maximum light intensity transmitted was higher and found to be 0.89 at zero phase difference. This value indicates a large phase delay and decreased to a non-zero value. At maximum electric field intensity, a ‘climbing’ of the nitrobenzene on the Kerr cell walls and electrodes was observed with more nitrobenzene attracted to the anode. The effect suspected to be of electrostatic origin may have been driven by the predominant ions in the nitrobenzene. Furthermore, the higher level of the nitrobenzene meniscus at the anode probably suggests that while the cathode injected carriers of negative charge into the liquid the injection of carriers from the anode was weaker. For better results, attention should be given to Polaroid quality, the purity of the liquid nitrobenzene and the length of the electrodes used.

Chiroptical activity of hydroxycarboxylic acids with implications for the origin of biological homochirality

Circularly polarised light (CPL) interacting with interstellar organic molecules might have imparted chiral bias and hence preluded prebiotic evolution of biomolecular homochirality. The l-enrichment of extra-terrestrial amino acids in meteorites, as opposed to no detectable excess in monocarboxylic acids and amines, has previously been attributed to their intrinsic interaction with stellar CPL revealed by substantial differences in their chiroptical signals. Recent analyses of meteoritic hydroxycarboxylic acids (HCAs) – potential co-building blocks of ancestral proto-peptides – indicated a chiral bias toward the l-enantiomer of lactic acid. Here we report on novel anisotropy spectra of several HCAs using a synchrotron radiation electronic circular dichroism spectrophotometer to support the re-evaluation of chiral biomarkers of extra-terrestrial origin in the context of absolute photochirogenesis. We found that irradiation by CPL which would yield l-excess in amino acids would also yield l-excess in aliphatic chain HCAs, including lactic acid and mandelic acid, in the examined conditions. Only tartaric acid would show “unnatural” d-enrichment, which makes it a suitable target compound for further assessing the relevance of the CPL scenario.

Rheological and structural properties of lecithin-based organogels

The objectives of this study were to develop lecithin-based organogels made of a biocompatible organic phase and to study the structural and rheological properties of organogels made with different organic phases. The materials used were soybean lecithin of >90% purity (phosphatidylcholine), distilled water and the following organic phases: isooctane (ISO), mineral oil (MO) and isopropylpalmitate (IPP). Phase diagrams for the PC/Water/ISO, PC/Water/ISO/MO (20:80 vo1/vo1), PC/Water/IPP,PC/Water/IPP/MO (50:50vo1/vo1 and 30:70vo1/vo1) and Pc/Water/MO systems were analysed using polarised light microscopy. A narrow region of organogel formation was observed in all systems at molar ratios of water to lecithin between values of 0.4 and 4, depending on the organic phase used. Small-angle X-ray diffraction studies for the PC/Water/ISO system revealed the existence of a highly ordered two-dimensional crystal lattice likely formed by the bundling of the cylindrical reverse micellar tubes. The results for the Pc/Water/IPP and PC/Water/MO systems indicated that there was not enough structural material in the organogels to observe any level of molecular organisation. In summary, this study demonstrated that it was possible to develop biocompatible lecithin-based organogels.

Rheological and structural properties of lecithin-based organogels

The objectives of this study were to develop lecithin-based organogels made of a biocompatible organic phase and to study the structural and rheological properties of organogels made with different organic phases. The materials used were soybean lecithin of >90% purity (phosphatidylcholine), distilled water and the following organic phases: isooctane (ISO), mineral oil (MO) and isopropylpalmitate (IPP). Phase diagrams for the PC/Water/ISO, PC/Water/ISO/MO (20:80 vo1/vo1), PC/Water/IPP,PC/Water/IPP/MO (50:50vo1/vo1 and 30:70vo1/vo1) and Pc/Water/MO systems were analysed using polarised light microscopy. A narrow region of organogel formation was observed in all systems at molar ratios of water to lecithin between values of 0.4 and 4, depending on the organic phase used. Small-angle X-ray diffraction studies for the PC/Water/ISO system revealed the existence of a highly ordered two-dimensional crystal lattice likely formed by the bundling of the cylindrical reverse micellar tubes. The results for the Pc/Water/IPP and PC/Water/MO systems indicated that there was not enough structural material in the organogels to observe any level of molecular organisation. In summary, this study demonstrated that it was possible to develop biocompatible lecithin-based organogels.

Histovariability and Palaeobiological Implications of the Bone Histology of the Dromornithid, Genyornis newtoni

The bone microstructure of extinct animals provides a host of information about their biology. Although the giant flightless dromornithid, Genyornis newtoni, is reasonably well known from the Pleistocene of Australia (until its extinction about 50–40 Ka), aside from various aspects of its skeletal anatomy and taxonomy, not much is known about its biology. The current study investigated the histology of fifteen long bones of Genyornis (tibiotarsi, tarsometatarsi and femora) to deduce information about its growth dynamics and life history. Thin sections of the bones were prepared using standard methods, and the histology of the bones was studied under normal and polarised light microscopy. Our histological analyses showed that Genyornis took more than a single year to reach sexual maturity, and that it continued to deposit bone within the OCL for several years thereafter until skeletal maturity was attained. Thus, sexual maturity and skeletal maturity were asynchronous, with the former preceding the latter. Our results further indicated that Genyornis responded to prevailing environmental conditions, which suggests that it retained a plesiomorphic, flexible growth strategy. Additionally, our analyses of the three long bones showed that the tibiotarsus preserved the best record of growth for Genyornis.