Number Of Lamellae Research Articles

Effect of Freeze-Thawing Process on the Size and Lamellarity of PEG-Lipid Liposomes

The influence of the freeze-thawing process on the size and lamellarity of multilamellar PEG-lipid liposomes prepared from a mixture of egg yolk phosphatidilcholine (EggPC) and distearoyl phosphatidylethanolamine polyethyle- neglycol (DSPE-PEG) 2000 was investigated. Trapped volume measurement, quasielastic light scattering (QELS) and freeze-fracture electron microscopy were used to estimate the morphology and lamellarity of liposomes. During the freeze-thawing process, the lamellarity of multilamellar vesicles (MLVs) depended strongly on both PEG-lipid concentra- tion and the number of freeze-thaw cycles. The decrease in the number of lamellae was a function of the number of freeze-thaw cycles. The increase in trapped volume coincided with the decrease in the number of lamellae observed in electron micrographs. After comparing the results obtained from EggPC/DSPE-PEG2000 MLV and from pure EggPC MLV, it was concluded that during the freeze-thawing the liposomes with DSPE-PEG2000 achieved a unilamellar structure more readily than the pure EggPC liposomes.

Structure, mechanical properties and degradation behaviors of the electrospun fibrous blends of PHBHHx/PDLLA

Blends of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) and poly( d, l-lactic acid) (PDLLA) with different ratios were fabricated into fibrous membranes by electrospinning processes. Suggested by DSC, WAXD, and SAXS results, the molecular chains of PHBHHx and PDLLA were partially mixed in the amorphous phase, PDLLA didn’t affect the growth of PHBHHx crystalline phase, and PDLLA was excluded from PHBHHx lamella stacks, i.e. in form of interstack segregation, in the blend fibrous matrix. The mechanical properties of the electrospun fibrous membranes depended on the orientation of fibers in the membranes. The electrospun membranes had higher elongation; furthermore, the tensile strength and modulus of the fibers within the membranes were higher than the corresponding cast membranes. As the content of PDLLA increased, the electrospun fibrous membranes of the blends showed higher elongation and lower tensile modulus due to the decreased number of lamellae. According to the change of molecular weight distribution, both PHBHHx and PDLLA portions in the electrospun blend membranes followed bulk erosion and PDLLA degraded faster than PHBHHx during the degradation process. The morphology change of the electrospun fibrous blends during the hydrolytic degradation indicated that the degradation behaviors were strongly influenced by the miscibility and the structural phase segregation of PHBHHx/PDLLA blend in the electrospun fibers.

Osteonic organization of limb bones in mammals, including humans, and birds: a preliminary study.

As it is well known, bone tissue is characterized by a calcified extracellular matrix which makes this tissue suitable to support the body and protect the inner organs. Lamellar bone tissue is organized in lamellae, 3-7 microm in thickness, and arranged concentrically around vascular channels: the basic structure in this type of organization is called Haversian system or osteon and the diameter of osteons depends on the number of lamellae. Shape and regional density of osteons are related to the bone segment and the specific functional requirements to meet. Aim of this study is to correlate the compact bone tissue microstructure in various classes of mammals, including humans, and birds in order to find an adequate identification key. The results of our study show that in bone tissue samples from various classes of mammals, including humans, and birds the osteonic structure shows peculiar features, often depending on the rate of bone remodelling, different in different animal species. We conclude that a careful microscopic analysis of bone tissue and the characterization of distinctive osteonic features could give a major contribution to forensic medicine to obtain a more reliable recognition of bone findings.

Olfactory morphology and physiology of elasmobranchs

Elasmobranch fishes are thought to possess greater olfactory sensitivities than teleost fishes due in part to the large amount of epithelial surface area that comprises their olfactory organs; however, direct evidence correlating the size of the olfactory organ to olfactory sensitivity is lacking. This study examined the olfactory morphology and physiology of five distantly related elasmobranch species. Specifically, we quantified the number of lamellae and lamellar surface area (as if it were a flat sheet, not considering secondary lamellae) that comprise their olfactory organs. We also calculated the olfactory thresholds and relative effectiveness of amino acid odorants for each species. The olfactory organs varied in both the number of lamellae and lamellar surface area, which may be related to their general habitat, but neither correlated with olfactory threshold. Thresholds to amino acid odorants, major olfactory stimuli of all fishes, ranged from 10⁻⁹·⁰ to 10⁻⁶·⁹ mol l⁻¹, which indicates that these elasmobranch species demonstrate comparable thresholds with teleosts. In addition, the relative effectiveness of amino acid stimuli to the olfactory organ of elasmobranchs is similar to that previously described in teleosts with neutral amino acids eliciting significantly greater responses than others. Collectively, these results indicate parallels in olfactory physiology between these two groups of fishes.

Self-Assembly of Lamellar- and Cylinder-Forming Diblock Copolymers in Planar Slits: Insight from Dissipative Particle Dynamics Simulations

We present a dissipative particle dynamics simulation study on nanostructure formation of symmetric and asymmetric diblock copolymers confined between planar surfaces. We consider symmetric and slightly asymmetric diblock copolymers that form lamellar nanostructures in the bulk, and highly asymmetric diblock copolymers that form cylindrical nanostructures in the bulk. The formation of the diblock copolymer nanostructures confined between the planar surfaces is investigated and characterized by varying the separation width and the strength of the interaction between the surfaces and the diblock copolymers. Both the slit width and the surface interaction strongly influence the phase diagram, especially for the asymmetric systems. For the symmetric and slightly asymmetric diblock copolymer systems, the confinement primarily affects the orientation of the lamellar domains and only marginally influences the domain morphologies. These systems form parallel lamellar phases with different number of lamellae, and perpendicular and mixed lamellar phases. In a narrow portion of the phase diagram, these systems exhibit a parallel perforated lamellar phase, where further insight into the appearance of this phase is provided through free-energy calculations. The confined highly asymmetric diblock copolymer system shows, in addition to nanostructures with parallel and perpendicular cylinders, noncylindrical structures such as parallel lamellae and parallel perforated lamellae. The formation of the various confined nanostructures is further analyzed by calculating structural characteristics such as the mean square end-to-end distance of the diblock copolymers and the nematic order parameter.

Changes in Mallard Anas platyrhynchos bill morphology after 30 years of supplemental stocking

Capsule Massive releases of captive‐reared Mallard for hunting purposes have been practiced for 30 years. During this period the number of lamellae per centimetre of bill length in wild Mallard populations has decreased. Aims Every year since the 1970s, several million captive Mallard have been released in Europe. This may lead to a spread of unnatural phenotypes into the wild. Nevertheless, the consequences of such introductions have not been examined. Methods Two widespread and common migratory ducks were studied: Mallard Anas platyrhynchos and Teal A. crecca. Mallard is the only duck species for which stocking programmes occur, and Teal served as a control. In a ‘before–after’ design, we compared duck bill lamellar density over the last 30 years. Results Lamellar density in Mallard, but not Teal, decreased. The observed 10% decrease occurred in the first (proximate) centimetre of the bill, the most crucial in terms of food filtration. Conclusions We hypothesize that the change in bill morphology was because of the propagation of captive Mallard into the wild: captive Mallard eat mainly large items, relaxing the natural selection pressure maintaining high lamellar density for sieving small prey in wild ducks.

The internal thoracic artery as a transitional type of artery: a morphological and morphometric study.

Coronary artery by-pass grafting (CABG) with arterial grafts is widely accepted as the procedure of choice in the treatment of coronary ischemic disease. It brings back focus on morphological studies of arteries used as conduits in this procedure. One of the most frequently used CABG grafts is the internal thoracic artery with an excellent graft prognosis and patency rate. The aim of the study was a detailed morphological and morphometric description of the internal thoracic artery with an emphasis on its basic histological structure and its changes in aging and atherosclerosis. Therefore, 42 full-length arteries were obtained during forensic autopsies from 27 persons, aged between 20 and 81 years, who had died from non-vascular causes. The arteries were classified into three different age groups. Analysis of the serial arterial segments has shown that the internal thoracic artery is an artery of the transitional type whose media is organized into two layers: the internal, muscular layer and the external layer with spirally oriented elastic lamellae and smooth muscle cells in between. The number of elastic lamellae progressively decreases throughout the length of the examined arteries. As opposed to previous assumptions, we have proven that the grade of atherosclerosis is independent of the number of elastic lamellae in the external media. Perfectly formed elastic lamellae are not a persistent feature of the internal thoracic artery, as previously claimed. We have confirmed that the thickness of elastic lamellae decreases, while the number and the size of their fenestrations steadily increase with aging.

Morphological adaptations to chronic hypoxia in deep-sea decapod crustaceans from hydrothermal vents and cold seeps

Animals inhabiting hydrothermal vents and cold seeps face conditions that are challenging for survival. In particular, these two habitats are characterized by chronic hypoxia, sometimes reaching complete anoxia. The characteristics of the scaphognathite and gills were studied in four species of shrimp and three species of crabs from hydrothermal vents and cold seeps, in order to highlight potential adaptations that could enhance oxygen acquisition in comparison with shallow-water relatives. All the vent and seep species studied here exhibit significantly larger scaphognathites, likely allowing more water to flow over their gills per stroke of this appendage. This is probably more energetically efficient that prolonged hyperventilation. In contrast to annelids, vent and seep decapods usually do not possess enlarged gills, a phenomenon likely due to the physical limitations imposed by the size of the gill chamber. In the vent shrimp Rimicaris exoculata and the vent crab Bythograea thermydron, however, there is a significantly higher specific gill surface area linked to a higher number of lamellae per gram of gill. Again in contrast to annelids, the diffusion distance through the gills is not strikingly different between the vent shrimp Alvinocaris komaii and the shallow-water species Palaemon spp. This may indicate that the epithelium and cuticle of the decapod gills are already optimized for oxygen uptake and that reducing the thickness of these compartments is not physically possible without affecting the physical integrity of the gills.

Functional morphology of the olfactory organ of the tongue sole, Cynoglossus semilaevis

The morphology and structure of the olfactory organ of Cynoglossus semilaevis Gunther are described. The oval olfactory sacs on both sides differ in size and in the number of lamellae, with those on the abocular side having smaller sacs and fewer lamellae than those on the ocular side. On the ocular side, the average ratio of sac length to eye diameter is 2.1 (i.e.>1) with an average of 91 lamellae, while on the abocular side, the values were 1.7 (i.e.>1) and 69, respectively. In addition, the surface morphology varies in different parts of the lamella. The frontal part, near the anterior nostril, is a non-sensory margin with cilia-free epidermal cells. Within this is an internal ciliated sensory area, which is intercalated with ciliated receptor cells and a few ciliated non-sensory cells. Additionally, some dense ciliated non-sensory cells make up a non-sensory area, which also contains cilia-free epidermal cells distributed in patches. In the rear of the olfactory sac near the posterior nostril, the lamellae differ in morphology from those of the frontal olfactory sac but are similar in having few ciliated receptor cells. In other words, the surface of the lamellae in the rear part of the olfactory sac is mainly non-sensory. At present, four types of lamellae (I, II, III and IV) have been recognized in relation to the pattern of the sensory epithelium. In this study, the frontal and rear lamellae resembled types I and IV, respectively, but are referred to as types I′ and IV′ because they are slightly less developed. Data on the ratio of length of lamellae to eye diameter, number of lamellae and the type of surface pattern of the lamellae show that the development of the olfactory system of C. semilaevis facilitates prey capture.

Comparison of the Nasal Olfactory Organs of Various Species of Lizardfishes (Teleostei: Aulopiformes: Synodontidae) with Additional Remarks on the Brain

The olfactory organs of lizardfishes (Synodontidae) are situated in two capsules connected to the outside by incurrent and excurrent openings. The olfactory epithelium is in form of petal rosettes each composed of lamellae and a rephe, and bear olfactory receptor neurons, supporting cells and cells with kinocillia. The dimension of rosettes and lamellae, as well as the number of lamellae, increase with growth of the fish; until in adult fish these parameters remaine constant, species specific. In adultSynodusspp. andTrachinocephalus myopsthe rosettes are 3.5–4.0 mm long, with 5–8 lamellae, whereas inSauridaspp. they are 8.0 mm and possess up tp 22 lamellae. The number of ORN ranges from 2,600 on the smaller lamellae to 20,000 on the largest ones. The number of ORN/m of olfactory is ca. 30,000 inSauridaspp. Thus the rosettes ofS. macrolepiswith 20 lamellae possess a total of ca. 170,000 ORN, whereas those ofSy. variegatusandT. myopswith the average of six lamellae possess only ca. 50,000–65,000 ORN. The olfactory nerves lead from the rosettes to the olfactory balbs situated on the olfactory lobes. The differences among the species in olfactory organs are discussed in correlation with their distribution.

Microstructure Characteristics of the Cornea in Birds and Mammals

In this study, the microstructure of the cornea was compared among chickens (Gallus gallus), jungle crows (Corvus macrorhynchos), rats (Rattus norvegicus) and rabbits (Oryctolagus cuniculus). The density of keratocytes in the mammals was over 3 times that in the birds. The size of the keratocytes in the birds and rat were significantly lower than those in the rabbit. Using scanning and transmission electron microscopy, the bundles of collagen fibers in the birds were found to be well arranged, while those in the mammals were arranged randomly. The collagen lamellae of the birds were significantly thicker than those of the mammals, and the numbers of collagen lamellae in the birds were significantly smaller than in the mammals. The center-to-center distances between the collagen fibrils of the chicken and rabbit were significantly larger than those of the crow and rat. The densities of collagen fibrils in the chicken and rabbit were significantly less than those of the crow and rat.

Ribosome–Lamella Complexes in the Peripheral Blood of Patients with Chronic Lymphocytic Leukemia are Associated with Serological Immune Deficiency

The ribosome–lamella complex (RLC) is a cylindrical structure composed of different numbers of circular lamellae with associated particles, regarded as ribosomes, around a central core. Structures resembling RLC, but lacking the typical mature appearance of RLC, have been called pre-RLC. The authors have found RLCs and pre-RLCs in peripheral lymphocytes of 3 patients with chronic lymphocytic leukemia (CLL). The fact that CLL patients with RLCs were in early Rai clinical stages, had good clinical prognostic factors, and did not require immediate therapy indicates that RLCs occurred in the early course of some cases of CLL. Moreover, the presence of RLC was associated with hypogammaglobulinemia M.

Real Time Fluorescence Microscopy Observations of Dehydration-Induced Domain Formation in Raft Forming Multi Lamellar Lipid Stacks

Domain formation in multi-component lipid mixtures is a well-known phenomenon understood in terms of equilibrium phase separation of lipid components into distinct co-existing phases. Such phase-separated equilibrium domain morphologies have been extensively studied in mono- and bimolecular lipid configurations (e.g., Langmuir monolayers, and giant unilamellar vesicles), and to a lesser extent in multilamellar lipid configurations consisting of discrete, low number of lamellae (less than ten). We have run experiments that reveal pattern formation in thick lipid stacks consisting of several thousand lamellae. We observe the appearance of domains when a lipid cake - pre-hydrated by a prolonged exposure to humid air - are left standing in laboratory air. The domain patterns develop in concert with the evaporation of water from a nominally wet pre-hydrated lipids consisting of putative raft forming mixtures of egg-sphingomylein, Cholesterol, and DOPC. Our results suggest that the dehydration of water-saturated lipid stacks provides the driving force to induce the lateral phase separation of the lipid mixture into the so-called liquid-ordered (cholesterol and sphingomyelin-enriched) and liquid-disordered phases. Our experiments enable studies of the dynamics of the domain pattern formation and the interactions between domains (e.g., long-term fusion) at low hydrations. We use a combination of microscopy tools, including Atomic Force Microscopy, fluorescence confocal microscopy, and bright-field microscopy, to determine the influence of interaction between the line tension and key elastic properties of the lipid membrane on the characteristics of the domain patterns. The observed dehydration-induced phase separation may have important consequences for freeze-drying or desiccation of lipid mixtures and living cells.

Gill morphometrics in relation to gas transfer and ram ventilation in high‐energy demand teleosts: Scombrids and billfishes

This comparative study of the gill morphometrics in scombrids (tunas, bonitos, and mackerels) and billfishes (marlins, swordfish) examines features of gill design related to high rates of gas transfer and the high-pressure branchial flow associated with fast, continuous swimming. Tunas have the largest relative gill surface areas of any fish group, and although the gill areas of non-tuna scombrids and billfishes are smaller than those of tunas, they are also disproportionally larger than those of most other teleosts. The morphometric features contributing to the large gill surface areas of these high-energy demand teleosts include: 1) a relative increase in the number and length of gill filaments that have, 2) a high lamellar frequency (i.e., the number of lamellae per length of filament), and 3) lamellae that are long and low in profile (height), which allows a greater number of filaments to be tightly packed into the branchial cavity. Augmentation of gill area through these morphometric changes represents a departure from the general mechanism of area enhancement utilized by most teleosts, which lengthen filaments and increase the size of the lamellae. The gill design of scombrids and billfishes reflects the combined requirements for ram ventilation and elevated energetic demands. The high lamellar frequencies and long lamellae increase branchial resistance to water flow which slows and streamlines the ram ventilatory stream. In general, scombrid and billfish gill surface areas correlate with metabolic requirements and this character may serve to predict the energetic demands of fish species for which direct measurement is not possible. The branching of the gill filaments documented for the swordfish in this study appears to increase its gill surface area above that of other billfishes and may allow it to penetrate oxygen-poor waters at depth.

In Situ Follow-Up of the Intercalation Process in a Clay/Polymer Nanocomposite Model System by Rheo-XRD Analyses

This work deals with the follow-up of structure evolution in clay−polymer nanocomposites during the intercalation process through in situ analyses combining X-ray diffraction and rheology using a home-modified X-ray diffraction setup coupled with a rheometer with a special shearing cell developed for this work. To avoid any interference of medium elasticity, the selected matrix was a bisphenol A-based epoxy resin DGEBA with a Newtonian behavior under the examined experimental conditions. The selected clay was an organophilic montmorillonite (Cloisite 30B). The evolution of clay stacks in the clay−polymer nanocomposites was assessed under quiescent conditions by simultaneous time-resolved X-ray diffraction (XRD) and rheometry. The main results showed a very slow polymer diffusion process that increases the concentration of the intercalated stacks, narrows their distribution, and decreases the number of lamellae per stack.

Effect of additives on distributions of lamellar structures in sheared polymer: a study of synchrotron small-angle x-ray scattering

The effects of additives on the distributions of lamellar morphology and orientation in sheared isotactic polypropylene were investigated using the small beam of synchrotron small-angle x-ray scattering. The Cu-phthalocyanine can template the lamellar orientation even under low shear rates, whereas the ultramarine blue cannot. The surface contact is suggested to play a role in stabilizing the formation of oriented nuclei which subsequently direct the growth of oriented lamellae. The additives have no notable effects on the long spacing in the shear region. However, at high shear rates, they decrease the thickness of crystalline lamellae or increase the thickness of amorphous lamellae. Since the additives increase the degree of volume crystalline in the shear region, the number of crystalline lamellae should be increased. The results are helpful in designing and selecting suitable additives for controlling lamellar morphology and orientation.

The role of olfaction throughout juvenile development: Functional adaptations in elasmobranchs

Seven elasmobranch species, a group known for their highly-developed sense of smell, were examined for developmental changes in the number of olfactory lamellae, the size of the surface area of the sensory olfactory epithelium and the mass of both the olfactory rosettes (primary input to the CNS), and the olfactory bulbs. Within each species, juveniles possessed miniature versions of the adult olfactory organs, visually not distinguishable from these and without any obvious structural differences (e.g., with respect to the number of lamellae and the extent of secondary folding) between differently sized individuals. The size of the olfactory organs was positively correlated with body length and body mass, although few species showed proportional size scaling. In Aetobatus narinari and Aptychotrema rostrata, olfactory structures increased in proportion to body size. With respect to the growth of the olfactory bulb, all species showed allometric but not proportional growth. Olfaction may be of particular importance to juveniles in general, which are often subjected to heavy predation rates and fierce inter/intraspecific competition. Accordingly, it would be advantageous to possess a fully functional olfactory system early on in development. Slow growth rates of olfactory structures could then be attributed to a greater reliance on other sensory systems with increasing age or simply be regarded as maintaining an already optimized olfactory system.

Self-Assembly of Symmetric Diblock Copolymers in Planar Slits with and without Nanopatterns: Insight from Dissipative Particle Dynamics Simulations

We present a dissipative particle dynamics simulation study on the formation of nanostructures of symmetric diblock copolymers confined between planar surfaces with and without nanopatterns. The nanopatterned surface is mimicked by alternating portions of the surface that interact differently with the diblock copolymers. The formation of the diblock-copolymer nanostructures confined between the planar surfaces is investigated and characterized by varying the separation width and the strength of the interaction between the surfaces and the diblock copolymers. For surfaces with nanopatterns, we also vary both the mutual area and location of the nanopatterns, where we consider nanopatterns on the opposing surfaces that are vertically (a) aligned, (b) staggered, and (c) partially staggered. In the case of planar slits without nanopatterns, we observe the formation of perpendicular and parallel lamellar phases with different numbers of lamellae. In addition, the symmetric diblock copolymers self-assemble into adsorbed layer and adsorbed layer-parallel lamellar phases and a mixed lamellar phase when the opposing surfaces of the planar slits are modeled by different types of wall beads. In the case of nanopatterned planar slits, we observe novel nanostructures and attempt to rationalize the diblock copolymer self-assembly on the basis of the behavior that we observed in the planar slits without nanopatterns. In particular, we investigate the applicability of predicting the structures formed in the nanopatterned slits by a superposition of the observed structures in slits without nanopatterns.

Alterations in Aortic Cellular Constituents during Thoracic Aortic Aneurysm Development: Myofibroblast-Mediated Vascular Remodeling

The present study tested the hypothesis that changes in the resident endogenous cellular population accompany alterations in aortic collagen and elastin content during thoracic aortic aneurysm (TAA) development in a murine model. Descending thoracic aortas were analyzed at various time points (2, 4, 8, and 16 weeks) post-TAA induction (0.5 M CaCl2, 15 minutes). Aortic tissue sections were subjected to histological staining and morphometric analysis for collagen and elastin, as well as immunostaining for cell-type-specific markers to quantify fibroblasts, myofibroblasts, and smooth-muscle cells. Results were compared with reference control mice processed in the same fashion. Aortic dilatation was accompanied by changes in the elastic architecture that included: a decreased number of elastic lamellae (from 6 to 4); altered area fraction of elastin (elevated at 4 weeks and decreased at 16 weeks); and a decreased area between elastic lamellae (minimum reached at 4 weeks). Total collagen content did not change over time. Increased immunoreactivity for fibroblast and myofibroblast markers was observed at 8- and 16-week post-TAA-induction, whereas immunoreactivity for smooth-muscle cell markers peaked at 4 weeks and returned to baseline by 16 weeks. Therefore, this study demonstrated that changes in aortic elastin content were accompanied by the emergence of a subset of fibroblast-derived myofibroblasts whose altered phenotype may play a significant role in TAA development through the enhancement of extracellular matrix proteolysis.

The evaluation of age-related histomorphometric variables in a cadaver sample of lower socioeconomic status: implications for estimating age at death

Estimating age at death from adult skeletal remains is a daunting task for human osteologists. For this reason, the evaluation of micro-structural changes in bone with advancing age has become a popular method. However, factors such as nutrition, chronic disease, population group and sex have been suggested to influence the rate of bone turnover, and thus the use of histological methods in providing an accurate age at death has been questioned. The purpose of this study was to evaluate the accuracy and repeatability of 10 histomorphometric traits used to estimate age. The sample comprised of 146 dissection room cadavers of known sex, age and ancestry (105 males and 41 females). A 0.2 cm × 1.0 cm sample was removed from the anterior surface of the mid-shaft of the femur (opposite the linea aspera), and slides were prepared according to standard methodology. The total osteon count ( r = 0.50), the percentage unremodelled bone ( r = −0.50), the total number of non-Haversian canals ( r = −0.50) and the average percentage of fragmental bone ( r = 0.55) had moderate correlations with age, while the total number of measurable osteons ( r = 0.43), the total number of osteonal fragments ( r = 0.40), the percentage of fragmentary bone ( r = 0.37) the average number of lamellae per osteon ( r = 0.29), the minimum diameter of the Haversian canals ( r = 0.14) and resorption spaces ( r = 0.11) had little to no relationship with age. Despite poor correlations with age, eight variables were shown to be highly repeatable ( r = 0.74–0.93). Moderate to low correlations with age may be attributed to these variables not being related to age in a progressive and predictable fashion, activity patterns or possible chronic disease in the sample. A databank needs to be compiled from larger samples from various populations in order to more holistically assess the relationship between these variables and age as well as other mitigating factors such as disease, nutrition and population group.