Simple Tubular Structure Research Articles

Intestinal remodeling during Xenopus metamorphosis as a model for studying thyroid hormone signaling and adult organogenesis

Intestinal development takes places in two phases, the initial formation of neonatal (mammals)/larval (anurans) intestine and its subsequent maturation into the adult form. This maturation occurs during postembryonic development when plasma thyroid hormone (T3) level peaks. In anurans such as the highly related Xenopus laevis and Xenopus tropicalis, the larval/tadpole intestine is drastically remodeled from a simple tubular structure to a complex, multi-folded adult organ during T3-dependent metamorphosis. This involved complete degeneration of larval epithelium via programmed cell death and de novo formation of adult epithelium, with concurrent maturation of the muscles and connective tissue. Here, we will summarize our current understanding of the underlying molecular mechanisms, with a focus on more recent genetic and genome-wide studies.

Bio-Inspired Fractal Robust Hydrogel Catheter for Intra-Abdominal Sepsis Management.

To deal with intra-abdominal sepsis, one of the major global causes of death in hospitalized patients, efficient abscess drainage is crucial. Despite decades of advances, traditional catheters have demonstrated poor drainage and absorption properties due to their simple tubular structures and their dense nonporous surface. Herein, inspired by porous sponges and fractal roots, a multifaceted hydrogel catheter with effective drainage, absorptive, and robust properties, is presented. Its unique fractal structures provide extensive internal branching and a high specific surface area for effective drainage, while the hierarchical porous structures provide a wide range of absorption capabilities. Additionally, its distinctive multi-interpenetration network maintains robust and appropriate mechanical properties, even after absorption multiple times of liquid and mechanical disturbance, allowing for intact removal from the abdominal cavity without harm to the animal in vivo. Besides, the loaded antimicrobial peptides are capable of being released in situ to inhibit the potential for infections. In vivo experiments have demonstrated that this hydrogel catheter efficiently removes lethal abscesses and improves survival. It is believed that this innovative and practical catheter will create a future precedent for hydrogel drainage devices for more effective management of intra-abdominal sepsis.

Additions to earthworms (Annelida, Crassiclitellata) from Aragua and Miranda states, Venezuela

Two new species of the earthworm genus Pontoscolex found in San Casimiro County, northern Venezuela are described. Because of some morphological variability, and to improve the previous description, we redescribe Onychochaeta windlei and Rhinodrilus fuenzalidae collected at La Cortada settlement, Miranda state. Pontoscolex (Mesoscolex) juanae sp. n. and Pontoscolex (Nulloscolex) hugoi subgen. n., sp. n have three pairs of tiny calciferous glands in 7th to 9th segments, with a simple tubular structure similar to that of the genus Onychochaeta; however, testes and funnels are enclosed in sacs in the 11th segment similar to the Pontoscolex. We also report the occurrences of Pontoscolex (Pontoscolex) corethrurus Müller, 1857, Metaphire houlleti (Perrier, 1872), Perionyx excavatus Perrier, 1872, Dichogaster bolaui (Michaelsen, 1891), and Eisenia fetida (Savigny, 1826).

Shallow-water hydrothermal venting and the formation of Precambrian ironstones: Insights from the terminal-Paleoproterozoic Xuanlong ironstones in North China Craton

Xuanlong ironstones occur as stromatolitic or ooidal, hematite-rich, concordant bodies in the Paleoproterozoic Chuanlinggou Formation of North China. Continental-derived iron was traditionally suggested as the ironstone source. However, widespread hydrothermal discharge chimney structures have been discovered. These structures are interpreted as fluid-flow pathways resulting from the ejection of hydrothermal fluids into unconsolidated sandy sediments in a shallow subtidal zone. Simple tubular and curviplanar structures outlined by the occurrence of Fe-rich silicified sediments are well-developed in the underlying sandstones. Honeycomb-like cavities and possible fluid-flow channel textures attest to primary porosity during the formation of the ironstones, indicating that hydrothermal fluids play a key role in the formation of ironstones. This study provides an unequivocal example of Paleoproterozoic shallow-water hydrothermal activity for the first time, which is of great significance in understanding the genesis of granular or Superior-type IFs in general.

Molecular crosstalk in tracheal development and its recurrence in adult tissue regeneration.

The trachea is a rigid air duct with some mobility, which comprises the upper region of the respiratory tract and delivers inhaled air to alveoli for gas exchange. During development, the tracheal primordium is first established at the ventral anterior foregut by interactions between the epithelium and mesenchyme through various signaling pathways, such as Wnt, Bmp, retinoic acid, Shh, and Fgf, and then segregates from digestive organs. Abnormalities in this crosstalk result in lethal congenital diseases, such as tracheal agenesis. Interestingly, these molecular mechanisms also play roles in tissue regeneration in adulthood, although it remains less understood compared with their roles in embryonic development. In this review, we discuss cellular and molecular mechanisms of trachea development that regulate the morphogenesis of this simple tubular structure and identities of individual differentiated cells. We also discuss how the facultative regeneration capacity of the epithelium is established during development and maintained in adulthood.

Sex cord-stromal tumor with annular tubules of the ovary – a case report

Sex cord-stromal tumors with annular tubules (SCTAT) of the ovary are rare. They have two clinicalpresentation forms: the syndromic form which is associated with Peutz-Jeghers syndrome and thenon-syndromic form which is frequently seen in the second or third decades. We describe a 25-year-old patient who underwent exploratory laparotomy. Macroscopically large ovarian mass was24.5×24×8 cm in diameter, encapsulated, congested, and lobulated. On the cut section, it wasgreyish with small cystic and hemorrhagic areas. Microscopically, the tumor mass is composed ofmany simple and complex tubular structures that have eosinophilic PAS-positive hyaline globules inthe center and are surrounded by peripheral palisading of the cells. Finally, the tumor was diagnosedas non-syndromic ovarian SCTAT.

Effect of silica supports on deoxygenation of methyl palmitate over mesoporous silica-supported Ni/Al catalysts

To develop an efficient catalyst for deoxygenation (DO) as the first step in biojet fuel production with silica-supported Ni/Al catalysts, the effects of silica supports were investigated in terms of pore structure, acidity, and pore size. The pore structures of silica were covered from microporous SiO2 to mesoporous SBA-15, SBA-16, and KIT-6. Then, taking a simple tubular structure of Ni/Al-SBA-15 with the best biojet fuel yield, samples with various acidity and pore sizes were further prepared through manipulation of the amount of aluminum (Al)-incorporation and the temperature of hydrothermal synthesis, respectively. The DO reactivity of the prepared silica-supported Ni/Al catalysts was assessed with methyl palmitate as a model compound of biomass feedstock. Based on the altered physicochemical properties of not only the silica support but also the supported Ni, the relationship between the variation of silica supports and their DO catalytic properties was investigated. This work provides a better understanding of silica-supported Ni/Al catalysts and how to design selective catalysts for DO reaction to maximize the biojet fuel hydrocarbon yield.

Physical and Mechanical Forces that Shape Heart Tube in the Chick Embryo

In the embryo, the heart is initially a simple tubular structure that undergoes complex morphological changes. This work focuses on the mechanisms that create the heart tube (HT). The early embryo is composed of three relatively flat primary germ layers called endoderm, mesoderm, and ectoderm. Endoderm and pre-cardiac cells located within bilateral regions of the mesoderm called heart fields (HFs) fold and fuse along the embryonic midline. Then both layers lengthen axially as the anterior intestinal portal (AIP) moves downward. Finally, the fused HFs thicken and expand to create the HT. Here, we combine experiments on chick embryos with computational modeling to explore physical mechanisms of heart tube formation. According to our hypothesis, differential anisotropic growth between mesoderm and endoderm drives ventral folding, and contraction along the AIP generates tension to elongate the HT. We test this hypothesis using biochemical perturbations of cell proliferation and contractility, as well as computational modeling. In embryos exposed to the mitotic inhibitor aphidicolin, little or no folding occurred, confirming that cell proliferation is required to initiate folding of HFs. To determine the effects of actomyosin contraction, we cultured Hamburger-Hamilton stage 5 embryos in media containing the myosin inhibitor blebbistatin. During incubation, folding occurred in treated embryos, but AIP descension proceeded at a progressively slower rate, showing that AIP downward motion is generated mainly by AIP contraction. Simulating these mechanisms in our computational model produces morphology in reasonable agreement with experiments. For the last phase, adding circumferential growth causes the HF to expand, creating the primitive HT, while radial growth increases the thickness of the heart wall. In conclusion, results of our study support our hypothesis for the creation of the heart tube.

A simple auxetic tubular structure with tuneable mechanical properties

Auxetic materials and structures are increasingly used in various fields because of their unusual properties. Auxetic tubular structures have been fabricated and studied due to their potential to be adopted as oesophageal stents where only tensile auxetic performance is required. However, studies on compressive mechanical properties of auxetic tubular structures are limited in the current literature. In this paper, we developed a simple tubular structure which exhibits auxetic behaviour in both compression and tension. This was achieved by extending a design concept recently proposed by the authors for generating 3D metallic auxetic metamaterials. Both compressive and tensile mechanical properties of the auxetic tubular structure were investigated. It was found that the methodology for generating 3D auxetic metamaterials could be effectively used to create auxetic tubular structures as well. By properly adjusting certain parameters, the mechanical properties of the designed auxetic tubular structure could be easily tuned.

Gaining insight of fetal brain development with diffusion MRI and histology

Human brain is extraordinarily complex and yet its origin is a simple tubular structure. Its development during the fetal period is characterized by a series of accurately organized events which underlie the mechanisms of dramatic structural changes during fetal development. Revealing detailed anatomy at different stages of human fetal brain development provides insight on understanding not only this highly ordered process, but also the neurobiological foundations of cognitive brain disorders such as mental retardation, autism, schizophrenia, bipolar and language impairment. Diffusion tensor imaging (DTI) and histology are complementary tools which are capable of delineating the fetal brain structures at both macroscopic and microscopic levels. In this review, the structural development of the fetal brains has been characterized with DTI and histology. Major components of the fetal brain, including cortical plate, fetal white matter and cerebral wall layer between the ventricle and subplate, have been delineated with DTI and histology. Anisotropic metrics derived from DTI were used to quantify the microstructural changes during the dynamic process of human fetal cortical development and prenatal development of other animal models. Fetal white matter pathways have been traced with DTI-based tractography to reveal growth patterns of individual white matter tracts and corticocortical connectivity. These detailed anatomical accounts of the structural changes during fetal period may provide the clues of detecting developmental and cognitive brain disorders at their early stages. The anatomical information from DTI and histology may also provide reference standards for diagnostic radiology of premature newborns.

SU‐E‐I‐73: Using Radial Basis Functions with Compact Support and Total Variations Regularization for Deformable Registration of Fetal MR Images

Purpose: The human brain is extraordinarily complex, and yet its origin is a simple tubular structure. Characterizing its anatomy at different stages of human fetal brain development not only aids in understanding this highly ordered process but also provides clues to detecting abnormalities caused by genetic or environmental factors. magnetic resonance images (MRI) has been used for quantitative studies of brain development in utero. However, non‐rigid registration of a sequence of MRI volumes remains to be a challenging problem. The authors present our recent results on the development of a computationally inexpensive radial basis functions (RBF) and total‐variation (TV) regularization algorithm for elastic alignment of MRI images. Methods: Our algorithm based on the landmarks and radial basis function with compact support,to registration of MR images which have an improved locality,allow to constrain elastic deformations to image parts where required .Then total‐variation regularization to account for the motion discontinuity close to the contact surface between fetal and uterus wall. The algorithm has been compared to the symmetric forces Demons methods. Results: Using a series of validation experiments on fetal cases. The authors demonstrate that using RBF with compact to find the region of interest (ROI) then using total variation registration techniques can all recover volume deformations in MRI image series with reasonable accuracy;Moreover,The proposed total variation registration technique has substantial computational advantage over the other approaches. Conclusion: The proposed RBF and TV registration technique has the potential for implementation on a computationally inexpensive platform and has the capability of recovering non‐rigid deformations in tissue with reasonable accuracy. This work is supported in part by grants from National Natural Science Foundation of China (NSFC: 81171402), NSFC Joint Research Fund for Overseas Research Chinese, Hong Kong and Macao Young Scholars (30928030), National Basic Research Program 973 (2010CB732606) from Ministry of Science and Technology of China, Guangdong Innovative Research Team Program (No. 2011S013) of China, Science and Technological Program for Dongguan's Higher Education, Science and Research, and Health Care Institutions(Grant No.2011108101001), and grant Comprehensive Strategic Cooperation Project of Guangdong province and Chinese academy of sciences (Grant No.2011B090300079).

Tokens of love: possible diagnostic value of mating plugs and refractive secretory uterine structures in Trichodorus (Diphtherophorina: Trichodoridae)

Within the Trichodoridae, mating plugs have only been recorded from Trichodorus species. They can be observed as a clear plug within the vagina/vulva but may also be present in the uteri. These secretory structures are diverse in size, varying between 4 and 27 μm in length, and in shape from simple unipartite tubular structures to bipartite with a central indentation or with a tail-like end. All mating plugs possess a central canal that can vary in diameter. Within Trichodorus, the shape and structure of the mating plugs can provide additional diagnostic information at species level.

Delineating Neural Structures of Developmental Human Brains with Diffusion Tensor Imaging

The human brain anatomy is characterized by dramatic structural changes during fetal development. It is extraordinarily complex and yet its origin is a simple tubular structure. Revealing detailed anatomy at different stages of brain development not only aids in understanding this highly ordered process, but also provides clues to detect abnormalities caused by genetic or environmental factors. However, anatomical studies of human brain development during the fetal period are surprisingly scarce and histology-based atlases have become available only recently. Diffusion tensor imaging (DTI) measures water diffusion to delineate the underlying neural structures. The high contrasts derived from DTI can be used to establish the brain atlas. With DTI tractography, coherent neural structures, such as white matter tracts, can be three-dimensionally reconstructed. The primary eigenvector of the diffusion tensor can be further explored to characterize microstructures in the cerebral wall of the developmental brains. In this mini-review, the application of DTI in order to reveal the structures of developmental fetal brains has been reviewed in the above-mentioned aspects. The fetal brain DTI provides a unique insight for delineating the neural structures in both macroscopic and microscopic levels. The resultant DTI database will provide structural guidance for the developmental study of human fetal brains in basic neuroscience, and reference standards for diagnostic radiology of premature newborns.

Anatomical Characterization of Human Fetal Brain Development with Diffusion Tensor Magnetic Resonance Imaging

The human brain is extraordinarily complex, and yet its origin is a simple tubular structure. Characterizing its anatomy at different stages of human fetal brain development not only aids in understanding this highly ordered process but also provides clues to detecting abnormalities caused by genetic or environmental factors. During the second trimester of human fetal development, neural structures in the brain undergo significant morphological changes. Diffusion tensor imaging (DTI), a novel method of magnetic resonance imaging, is capable of delineating anatomical components with high contrast and revealing structures at the microscopic level. In this study, high-resolution and high-signal-to-noise-ratio DTI data of fixed tissues of second-trimester human fetal brains were acquired and analyzed. DTI color maps and tractography revealed that important white matter tracts, such as the corpus callosum and uncinate and inferior longitudinal fasciculi, become apparent during this period. Three-dimensional reconstruction shows that major brain fissures appear while most of the cerebral surface remains smooth until the end of the second trimester. A dominant radial organization was identified at 15 gestational weeks, followed by both laminar and radial architectures in the cerebral wall throughout the remainder of the second trimester. Volumetric measurements of different structures indicate that the volumes of basal ganglia and ganglionic eminence increase along with that of the whole brain, while the ventricle size decreases in the later second trimester. The developing fetal brain DTI database presented can be used for education, as an anatomical research reference, and for data registration.

Circulating monocytic cells (MCs) and restoration of capillaries lost from the alveolar‐capillary membrane

We have reported loss of pulmonary capillaries in the adult lung in hyperoxia-induced pulmonary hypertension; and restoration of capillaries throughout the alveolar-capillary membrane on return to air breathing (Cell Tissue Res 2000, 300:263–284). We now report the role of blood-derived cells in this angiogenic process. Rats breathed at FiO2 0.87 for 28 days, FiO2 0.87 - 0.21 for 7 days and then FiO2 0.21 for 1, 2 or 4 weeks. In high-resolution images of patent capillary segments, VEGF-R2+ MCs were identified circulating free within the lumen in normal lung and in contact with endothelial cells (ECs) on return to air breathing (~1000 cells in 1474 segments). On attachment to ECs, the lamellapodia along the apical membrane of MCs extended into the EC cytosol as the cells extruded into the alveolar-capillary membrane’s interstitium. We reconstructed ~90 capillary segments re-forming in the first weeks of air breathing, each consisting of 20–25 digital images. MCs extended long cytoplasmic processes into thin regions of the membrane that, in the absence of a capillary segment, were filled with a fine collagenous matrix. The discontinuous channels initially formed by MC processes evolved into simple tubular structures. As lumen size increased, the matrix filling the slit-like lumen of the growing sprout was replaced by plasma-rich fluid, indicating connection to other patent units before erythrocytes confirmed blood flow. We conclude that in the hyperoxia-adapted lung, capillary growth triggered by return to air breathing (relative hypoxia) is accomplished by blood-derived MCs. Supported by NIH HLR01 070866.

Morphogenesis of the rat forebrain

Developmental process that leads to final forebrain shaping is a result of complex histogenetic and morphogenetic events. Comprehensions about brain development are based on observations carried out on onthogenetic successive stages. Microscopic analysis of brain together with analysis of serial sections gives information about shape the of some forebrain parts and basic relations between them. The aim of this study was to analyse morphogenesis in the earliest stages of rat's forebrain development. Rat brains used in this study were obtained from Fisher inbred rats with accurately timed pregnancies. The investigation was carried out on serial frontal sections of rat embryonic heads from the 12th (E12) to the 16th (E16) day of gestation. Gestation was considered to have begun early in the morning when sperm was found in the vaginal smear. Histological paraffin and plastic sections were systematically inspected with regard to morphogenetic changes of the forebrain parts telencephalon and diencephalon. E12: neural tube is completely closed in its cranial part. Rostral part of forebrain shows telencephalons vesicles origins as slightly paired enlargements of neuroepithelial wall. Between telencephalic vesicles origin and in direction to caudal there is an origin of diencephalon. E13: rostral part of forebrain shows well expressed and divided areas of telencephalons vesicles as basal, basolateral, dorsal and medial telencephalon. Central area between paired vesicles is a telencephalon impar. In diencephalon optic vesicles appeared. Epithalamus, thalamus and hypothalamus origins are slight enlargements of its neuroepithelial wall. E14: telencephalic vesicles spread above telencephalon impar into rostral direction and above diencephalon in rostrodorsal direction. Their basolateral parts of are very thickened and become folded. Sulcus telodiencephalicus appears. E15: the main event is the appearance of the origins of plexus choroideus in the area of telencephalon impar as fingerlike processes. E16: all forebrain parts, especially telencephalic vesicles-origin of brain hemispheres and processes of plexus choroideus, are progressively growing and shaping. Our morphologic analysis describes significant morphogenetic changes in the forebrain shape. The forebrain changes from a relatively simple tubular structure with thin walls surrounding a large ventricular system to a thick-walled brain with a highly convoluted but reduced ventricular system.

Belief vs. scientific observation: the curious story of the precardiac mesoderm.

Belief vs. scientific observation: the curious story of the precardiac mesoderm.

Developmental remodeling and shortening of the cardiac outflow tract involves myocyte programmed cell death.

The embryonic outflow tract is a simple tubular structure that connects the single primitive ventricle with the aortic sac and aortic arch arteries. This structure undergoes a complex sequence of morphogenetic processes to become the portion of the heart that aligns the right and left ventricles with the pulmonary artery and aorta. Abnormalities of the outflow tract are involved in many clinically significant congenital cardiac defects; however, the cellular and molecular processes governing the development of this important structure are incompletely understood. Histologic and tissue-tagging studies indicate that the outflow tract tissues compact and are incorporated predominantly into a region of the right ventricle. The hypothesis tested in the current study was that cell death or apoptosis in the muscular portion of the outflow tract is an important cellular mechanism for outflow tract shortening. The tubular outflow tract myocardium was specifically marked by infecting myocytes of the chicken embryo heart with a recombinant replication-defective adenovirus expressing beta-galactosidase (beta-gal) under the control of the cytomegalovirus promoter. Histochemical detection of the beta -gal-labeled outflow tract myocytes revealed that the tubular structure shortened to become a compact ring at the level of the pulmonic infundibulum over several days of development (stages 25-32, embryonic days 4-8). The appearance of apoptotic cardiomyocytes was correlated with OFT shortening by two histologic assays, TUNEL labeling of DNA fragments and AnnexinV binding. The rise and fall in the number of apoptotic myocytes detected by histologic analyses paralleled the change in activity levels of Caspase-3, a protease in the apoptotic cascade, measured in outflow tract homogenates. These results suggest that the elimination of myocytes by programmed cell death is one mechanism by which the outflow tract myocardium remodels to form the proper connection between the ventricular chambers and the appropriate arterial trunks.

Differential expression of two zebrafish emx homeoprotein mRNAs in the developing brain

The complete amino-acid sequences of two zebrafsh emx homeoproteins containing a homeodomain homologous to that of the Drosophila empty spiracles head gap gene product have been determined by cloning and sequencing of cDNAs. The zebrafish mex1 and emx2 homeoproteins consist of 233 and 247 amino acids, respectively. The zebrafish emx1 and emx2 mRNAs are present at 12 h after fertilization, when the presumptive brain is in a simple tubular structure, and before first primary neurons appear. During brain development, the emx1 mRNA is localized in the dorsal telencephalon, whereas the emx2 mRNA is distributed in the dorsal telencephalon, parts of the diencephalon and the otocyst. The differential expression patterns of the two emx homeoprotein mRNAs may define the subdivisions of the zebrafish telencephalon.

Heart Development in Drosophila Requires the Segment Polarity Gene wingless

Mesoderm induction has been studied in many systems and some of the factors involved have been identified. Although the heart is mesodermal in origin, the molecular basis of heart development is essentially unknown. The Drosophila heart is a simple tubular structure similar to the early heart tube in vertebrates. The homeobox gene, tinman, has been shown to be crucial for heart formation in Drosophila. Several genes with considerable sequence similarities to tinman are expressed in cardiac primordial tissue of vertebrates and are likely to be required for heart development of higher organisms as well. In addition to transcriptional control factors, heart development might also depend on inductive signals. Here, we demonstrate that the gene wingless ( wg), which is known to specify segmental polarity and neuroblast identity in Drosophila, has a novel role in mesoderm development: wg function is specifically required for heart development. A temperature-sensitive mutation of wg was used to inactivate wg function during precise developmental time periods. Elimination of wg function for a short time period after gastrulation results in the selective loss of heart precursors, without significantly affecting the formation of the body wall or visceral muscles, although some pattern defects are observed. This developmental requirement of wg for cardiac organogenesis is distinct from its function in segmentation and neurogenesis. We conclude that wg signaling is a crucial component of heart formation.