Individual Tubules Research Articles

A Novel Method to Quantify Dentine Tubule Occlusion Applied to in situ Model Samples

Objectives: To develop an innovative computerised routine, in conjunction with a minimally destructive imaging technique, to quantify dentine tubule occlusion. Methods: Polished human dentine samples (n = 480) were brushed during a 4-day in situ study with two occlusion-based dentifrices, a sodium fluoride control dentifrice (1,450 ppm) or water. Samples were imaged with tandem scanning microscopy (TSM) and conventional scanning electron microscopy (SEM). The level of dentine patency was then assessed using a visual ordinal scale (‘standard') or quantitatively using a specially designed computational routine. Results: The occlusion-based dentifrice resulted in significantly less patent dentine than controls for the ‘standard' (p = 0.01) assessment, but not for computer analyses (p = 0.10). The correlation of the number of individual patent tubules counted visually and by the computational routine in calibrations and in the in situ study was ≥0.8. Conclusions: This study identified a new computer-based routine, capable of objectively quantifying the patency of dentine imaged by SEM and TSM.

Examination of the Subsarcolemmal Tubular System of Mammalian Skeletal Muscle Fibers

A subsarcolemmal tubular system network (SSTN) has been detected in skeletal muscle fibers by confocal imaging after the removal of the sarcolemma. Here we confirm the existence and resolve the fine architecture and the localization of the SSTN at an unprecedented level of detail by examining extracellularly applied tubular system markers in skeletal muscle fiber preparations with a combination of three imaging modalities: confocal fluorescence microscopy, direct stochastic optical reconstruction microscopy, and tomographic electron microscopy. Three-dimensional reconstructions showed that the SSTN was a dense two-dimensional network within the subsarcolemmal space around the fiber, running ∼500–600 nm underneath and parallel to the sarcolemma. The SSTN is composed of tubules ∼95 nm in width with ∼60% of the tubules directed transversely and >30% directed longitudinally. The deeper regular transverse tubules located at each A-I boundary of the sarcomeres branched from the SSTN, indicating individual transverse tubules that form triads are continuous with, but do not directly contact the sarcolemma. This suggests that the SSTN plays an important role in affecting the exchange of deeper tubule lumina with the extracellular space.

Klinefelter Syndrome

Klinefelter syndrome (KS) with the karyotype 47,XXY is one of the commonest types of congenital chromosomal disorder in males, with an incidence of 0.1% to 0.2% of newborn male infants. It causes hypogonadism and infertility. Until now, however, only about one-quarter of all persons with KS received the diagnosis during their lifetimes. Selective review of the literature. KS is caused by aneuploidy of the sex chromosomes. Small, firm testes, the manifestations of androgen deficiency (sparse development of male-pattern body hair, greater than average height, lack of libido, erectile dysfunction) and, in more than 90% of affected men, azoospermia are its main features in adults. Affected boys may have verbalization difficulties and problems with learning and socialization. KS is often accompanied by other disturbances such as gynecomastia, varicose veins, thrombosis, osteoporosis, the metabolic syndrome, type 2 diabetes, and epilepsy. The most important therapeutic measure is testosterone supplementation, which should be initiated if the testosterone concentration drops below 12 nmol/L and should be given as directed in the guidelines for the treatment of hypogonadism. This recommendation is made even though there have not been any randomized controlled trials documenting the efficacy of testosterone therapy in adolescents or young adults. In some cases, viable sperm can be obtained from individual testicular tubules by biopsy, so that these patients are able to become fathers. The diagnosis of KS would be less frequently missed if doctors were more aware of, and attentive to, its key manifestations, particularly the small, firm testes, erectile dysfunction, and the comorbidities mentioned above. If the diagnosis were made more often, patients would more often be able to receive early treatment, which would improve their quality of life.

Selfish Spermatogonial Selection: Evidence from an Immunohistochemical Screen in Testes of Elderly Men

The dominant congenital disorders Apert syndrome, achondroplasia and multiple endocrine neoplasia–caused by specific missense mutations in the FGFR2, FGFR3 and RET proteins respectively–represent classical examples of paternal age-effect mutation, a class that arises at particularly high frequencies in the sperm of older men. Previous analyses of DNA from randomly selected cadaveric testes showed that the levels of the corresponding FGFR2, FGFR3 and RET mutations exhibit very uneven spatial distributions, with localised hotspots surrounded by large mutation-negative areas. These studies imply that normal testes are mosaic for clusters of mutant cells: these clusters are predicted to have altered growth and signalling properties leading to their clonal expansion (selfish spermatogonial selection), but DNA extraction eliminates the possibility to study such processes at a tissue level. Using a panel of antibodies optimised for the detection of spermatocytic seminoma, a rare tumour of spermatogonial origin, we demonstrate that putative clonal events are frequent within normal testes of elderly men (mean age: 73.3 yrs) and can be classed into two broad categories. We found numerous small (less than 200 cells) cellular aggregations with distinct immunohistochemical characteristics, localised to a portion of the seminiferous tubule, which are of uncertain significance. However more infrequently we identified additional regions where entire seminiferous tubules had a circumferentially altered immunohistochemical appearance that extended through multiple serial sections that were physically contiguous (up to 1 mm in length), and exhibited enhanced staining for antibodies both to FGFR3 and a marker of downstream signal activation, pAKT. These findings support the concept that populations of spermatogonia in individual seminiferous tubules in the testes of older men are clonal mosaics with regard to their signalling properties and activation, thus fulfilling one of the specific predictions of selfish spermatogonial selection.

Secreted VAPB/ALS8 Major Sperm Protein Domains Modulate Mitochondrial Localization and Morphology via Growth Cone Guidance Receptors

The VAPB/ALS8 major sperm protein domain (vMSP) is implicated in amyotrophic lateral sclerosis and spinal muscular atrophy, yet its function in the nervous system is not well understood. In Caenorhabditis elegans and Drosophila, the vMSP is cleaved from its transmembrane anchor and secreted in a cell type-specific fashion. We show that vMSPs secreted by neurons act on Lar-like protein-tyrosine phosphatase and Roundabout growth cone guidance receptors expressed in striated muscle. This signaling pathway promotes Arp2/3-dependent actin remodeling and mitochondrial localization to actin-rich muscle I-bands. C. elegans VAPB mutants have mitochondrial localization, morphology, mobility, and fission/fusion defects that are suppressed by Lar-like receptor or Arp2/3 inactivation. Hence, growth cone guidance receptor pathways that remodel the actin cytoskeleton have unanticipated effects on mitochondrial dynamics. We propose that neurons secrete vMSPs to promote striated muscle energy production and metabolism, in part through the regulation of mitochondrial localization and function.

Electron transfer kinetics at single-walled carbon nanotube paper: The role of band structure

The role of band structure of individual tubules from single-walled carbon nanotube paper in the electron transfer process was considered within Gerischer–Marcus theory using Raman scattering spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy data. A heterogeneous electron transfer rate of 1.06 × 10 − 3 cm s was observed for ferri/ferrocyanid. A position of the Raman radial breathing mode was used for determination of the chiral vectors of tubules being in resonance with excitation laser light of 1.17 eV. For these tubules, the calculated electron transfer rates are similar. It has been shown that nanotube electronic states away from the Fermi level contribute to the electron transfer kinetics due to the broad distribution of the redox states in electrolyte.

Vimentin expression in testes of Arabian stallions

Specific patterns of cytoskeletal filaments reflect a functional state of the cell. In testicular cells intermediate filaments (IFs) are of the vimentin type. Since it is known that Sertoli cells regulate the spermatogenic function in the male gonad, it became important to propose a system that could quantify the state of seminiferous tubular quality. To date, a Johnsen score system has never been used to equine testes. To demonstrate the expression pattern of vimentin in testes of mature Arabian stallions and correlate its distribution with grade of seminiferous tubule impairment as indicated by a Johnsen score. For histological examination by the Johnsen method, routine haematoxylin-eosin staining was used. Vimentin expression and its presence in testicular sections and testicular homogenates were detected by immunohistochemistry and western blot, respectively. Both analyses were performed qualitatively and quantitatively and further validated by ANOVA tests. Distinct morphology of seminiferous tubules was found in testes harvested from 3 stallions. Vimentin in IFs was immunolocalised to the cytoplasm of Sertoli, Leydig and peritubular-myoid cells. The intensity and pattern of the IFs staining was different in individual seminiferous tubules suggesting a correlation between vimentin expression and the severity of tubule degeneration. Qualitative results by immunohistochemistry and western blot were confirmed by further quantitative analyses. In equine testes, differential expression of vimentin was found to be correlated with the impairment of seminiferous tubules indicated by a decrease in Johnsen score. The Johnsen score system may be a useful method to facilitate the identification of tubular alterations in the stallion testes. Combined histological and immunohistochemical approach may provide a detailed phenotypic classification of stallions with decreased fertility.

Canonical Wnt9b signaling balances progenitor cell expansion and differentiation during kidney development

The mammalian kidney is composed of thousands of individual epithelial tubules known as nephrons. Deficits in nephron number are associated with myriad diseases ranging from complete organ failure to congenital hypertension. A balance between differentiation and maintenance of a mesenchymal progenitor cell population determines the final number of nephrons. How this balance is struck is poorly understood. Previous studies have suggested that Wnt9b/β-catenin signaling induced differentiation (mesenchymal-to-epithelial transition) in a subset of the progenitors but needed to be repressed in the remaining progenitors to keep them in the undifferentiated state. Here, we report that Wnt9b/β-catenin signaling is active in the progenitors and is required for their renewal/proliferation. Using a combination of approaches, we have revealed a mechanism through which cells receiving the same Wnt9b/β-catenin signal can respond in distinct ways (proliferate versus differentiate) depending on the cellular environment in which the signal is received. Interpretation of the signal is dependent, at least in part, on the activity of the transcription factor Six2. Six2-positive cells that receive the Wnt9b signal are maintained as progenitors whereas cells with reduced levels of Six2 are induced to differentiate by Wnt9b. Using this simple mechanism, the kidney is able to balance progenitor cell expansion and differentiation insuring proper nephron endowment. These findings provide novel insights into the molecular mechanisms that regulate progenitor cell differentiation during normal and pathological conditions.

Probing Chirality of a Lipid Tubular by Confocal Raman Microscopy

The chiral phospholipids 1,2-bis-(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (DC8,9 PC) can self assemble into lipid nanotubules. This hollow cylindrical supramolecular structure shows promise in a number of biotechnological applications. The mechanism of lipid tubule formation was initiated by assembling of lipid bilayer sheets from amphiphilic solution. Upon cooling, small ribbons were detached from the sheets and rolled up into helical tubules. The lipid tubules obtained were 0.6-0.8 microm in diameter and approximately 50 microm in length. Raman spectra of individual polymerized lipid tubules were measured by focused laser excitation of 532 nm leading to intense and reproducible Raman spectra. The chirality of lipid tubules was investigated by atomic force microscopy (AFM) and confocal Raman microscopy. We report the Raman mapping images revealing helical tubular profiles of C=C stretching and C[triple bond]C stretching of lipid tubules. Circular dichroism property of lipid tubules has also been probed with a 532 nm laser.

Mammary-type Tubulolobular Carcinoma of Anogenital Mammary-like Glands With Prominent Stromal Elastosis

To the Editor: Following the original description of mammary type tubulolobular carcinoma of the anogenital area, presumably originating in anogenital mammary-like glands (AGMLG) in 2006,7 we have recently observed a similar case. The neoplasm in this newly encountered case fulfilled the criteria for a tubulolobular carcinoma as defined in mammary pathology,5 and was almost identical to the original cutaneous example.7 Additionally, there was prominent stromal elastosis, a feature identical to that seen in association with invasive breast carcinomas, and not earlier recognized in carcinomas of the anogenital area. The patient was a 45-year-old female who presented with a 2-cm, asymptomatic solitary nodule in the vulva with unknown duration. Clinical investigation revealed no extracutaneous involvement; specifically, there was no mammary tumor. An enlarged lymph node in the right inguinal area was noted, but it proved negative on sentinel node biopsy, as did 2 other lymph nodes from the same region, and 3 left inguinal lymph nodes removed during a lymphadenectomy. After a wide surgical excision (specimen 4×2×1.2 cm), the patient is alive without signs of metastasis or recurrence at 4-year follow-up. Histopathologically, the tumor was composed of uniform round-to-ovoid cells arranged in a single-file pattern intermixed with areas manifesting round tubules often showing decapitation secretion at the luminal border. The neoplastic elements were arranged in a targetoid fashion or grew diffusely. The tubules were mainly composed of a single-cell layer without any evidence of a peripheral myoepithelial cell layer. Rare small solid aggregations were also noted. There were areas with perineural and intraneural invasion, especially in the foci, in which the tumor areas resembled an infiltrative lobular carcinoma (Figs. 1A–D). Immunohistochemically, the tumor cells in both ductal-like and lobular-like components reacted positively for E-cadherin. A remarkable feature was the prominent stromal elastosis emerging as clumps and masses of elastic material around individual neoplastic tubules (periductal elastosis) within the stroma (diffuse elastosis) and in association of vessel walls (vascular elastosis) highlighted by elastic stains (Fig. 1E, F). The residua of intact AGMLG were not recognized.FIGURE 1.: An infiltrative neoplasm in the dermis (A) containing areas with tubular formation and areas resembling infiltrative lobular carcinoma of the breast; areas of periductal, diffuse, and vascular elastosis can be discerned (B–D). Stromal elastosis is highlighted by elastic stains (E, F).In the breast, tubulolobular carcinoma was originally described as a tubular variant of lobular carcinoma,5 but many investigators nowadays regard neoplasm as a variant of invasive ductal carcinoma with a lobular growth pattern.2,12 There was only 1 earlier report of this tumor type in the skin.7 The neoplasm was suggested to originate from AGMLG, a normal constituent of the anogenital area, earlier considered to represent ectopic breast tissue.14 Lesions of AGMLG show a striking microscopic resemblance to their mammary counterparts.15 A majority of these lesions are epithelial or biphasic stromal epithelial neoplasms, including fibroadenoma and phyllodes tumors.8,9,10 Stromal changes in lesions of AGMLG seem to be also identical to those seen in their mammary counterparts. The most prominent stromal lesion is probably pseudoangiomatous stromal hyperplasia recognized in the anogenital area in 2005.6 In this case study, stromal elastosis seemed identical to that seen in mammary carcinomas. This feature is unusual for dermatopathologic cases. The prototype of the changes in the elastic tissue compartment, sometimes associated with cutaneous neoplasms, is a solar elastosis attributed to the degradation of collagen or elastic fibers owing to excessive sun exposure. Stromal elastosis in mammary carcinoma is an entirely different pathologic process characterized by the presence of excess elastic fibers in a diffuse manner within the stroma in the periductal location or around blood vessels. It is usually seen in invasive mammary carcinomas, especially ductal carcinomas but has been rarely found in benign lesions3 or even intact breast, wherein it is less prominent.4 Infiltrating neoplastic cells, when invading the basal lamina of the mammary ducts, are thought to stimulate periductal fibroblasts or myofibroblasts to produce elastic fibers.1,11,13 In normal circumstances, these cells are not engaged in elastic fibers production. Grossly, such stromal elastosis can be recognized as “chalky streaks.”1 This case of tubulolobular carcinoma of the vulva further highlights similarities between lesions of AGMLG and their mammary counterparts, including “secondary” stromal phenomena. Stromal elastosis is not a feature in invasive carcinomas of the skin, regardless of the histopathologic type. The likely explanation is that the stroma of AGMLG is physiologically different from the dermis and reacts to various stimuli in a manner similar to the mammary stroma. Maria Teresa Fernandez-Figueras, MD* Michal Michal, MD† Dmitry V. Kazakov, MD, PhD† *Department of Pathology Hospital Universitari Germans Trias i Pujol, Autonomous University of Barcelona Barcelona, Spain †Sikl's Department of Pathology Charles University Medical Faculty Hospital Pilsen, Czech Republic

MORPHOLOGICAL AND HISTOLOGICAL STUDY OF SUPERIOR LACRIMAL GLAND OF THIRD EYELID IN CAMEL (CAMELUS DROMEDARIUS)

Summary In this study ten pairs of superior gland of third eyelid of 10 adult male camels free of apparent ocular disease were examined to compare the normal anatomical and histological properties of these glands. After dissecting, all of the glands were characterized and measured (length and width) on both the left and right side. In the camels, the superior gland of the third eyelid was oval shaped and irregular in outline. The gland was located within the orbit on the medial aspect of the eyeball in animals that possess a nictitating membrane. Posterior surface of the gland was convex and attached to the nictitating membrane. The anterior surface that is contacted with the bulb of the eye was concave. The mean length of the superior gland of the third eyelid was 28.7 ± 2.7 mm and 27.2 ± 2.4 mm in the left and right side, respectively in the anteriorposterior direction. The mean width was 17.4 ± 0.8 mm and 16.1 ± 0.9 mm on the left and right side, respectively in the superior-inferior dimension. There was significant difference between the width of the left and right superior gland of the third eyelid. The mean width of the left superior gland was greater than the right (P<0.05). The histology of the gland revealed secretary units of tubuloacinar and serous with scattered alveolar units. Secretory cells had the typical appearance of serous cells. Tubuloacinar units completely surrounded the hyaline cartilage of the third eyelid. The Masson Trichrome stained connective tissue septae surround the individual acinus and tubules in camel superior gland. Larger sheets of connective tissue with inter and intralobular ducts as well as veins and arteriols were found and separated the gland into lobules.

Membrane Biogenesis: Networking at the ER with Atlastin

The peripheral endoplasmic reticulum forms a dynamic network of interconnected membrane tubules. Although some determinants of this striking architecture are known, the mechanism underlying fusion of individual tubules has remained elusive. Two studies now identify atlastin proteins as key mediators of homotypic fusion of endoplasmic reticulum membranes.

Effect of dentinal tubules and resin-based endodontic sealers on fracture properties of root dentin

Objective To investigate the role of dentinal tubules in the fracture properties of human root dentin and whether resin-filled dentinal tubules can enhance fracture resistance. Materials and methods Crack propagation in human root dentin was investigated in 200 μm thick longitudinal samples and examined by light and scanning electron microscopy. 30 maxillary premolar teeth were prepared for work of fracture ( Wf) test at different tubule orientations, one perpendicular and two parallel to dentinal tubules. Another 40 single canal premolars were randomly divided into four groups of 10 each: intact dentin, prepared but unobturated canal, canal obturated with epoxy rein (AH Plus™/gutta percha), or with UDMA resin sealer (Resilon ®/RealSeal ®). The samples were prepared for Wf test parallel to dentinal tubules. Wf was compared under ANOVA with statistical significance set at p < 0.05. Results Dentinal tubules influenced the path of cracks through dentin, with micro-cracks initiated in peritubular dentin of individual tubules ahead of the main crack tip. A significant difference ( p < 0.001) was found between Wf perpendicular to tubule direction (254.9 J/m 2) vs. parallel to tubule direction from inner to outer dentin (479.4 J/m 2). Neither canal preparation nor obturation using epoxy- or UDMA-based resins as sealer cements substantially influenced fracture properties of root dentin, despite extensive infiltration of dentinal tubules by both sealer cements.

Mitochondrial Cristae Revealed with Focused Light

Because of the diffraction resolution barrier, optical microscopes have so far failed in visualizing the mitochondrial cristae, that is, the folds of the inner membrane of this 200 to 400 nm diameter sized tubular organelle. Realizing a approximately 30 nm isotropic subdiffraction resolution in isoSTED fluorescence nanoscopy, we have visualized these essential structures in the mitochondria of intact cells. We find a pronounced heterogeneity in the cristae arrangements even within individual mitochondrial tubules.

Flat plastic embedding and precise longitudinal sectioning of isolated testicular seminiferous tubules.

A method is presented for the flat plastic embedding and precise longitudinal semithin sectioning of dissected individual seminiferous tubules. Following standard aldehyde- and OsO4-fixation, individual resin-immersed tubules are polymerized in an exactly flat position between the plan surfaces of a glass slide and an inverted pre-polymerized resin block. Each embedded tubule thus lies directly at the even surface of the resulting block and can subsequently be sectioned along its longitudinal course. The morphology of continuous, up to approximately 20 mm-long tubule segments may thus be immediately surveyed by high resolution light-microscopy and, if required, be studied at the ultrastructural level as well.

Superoxide dismutase activity along rat seminiferous epithelial wave: effects of ethane dimethanesulphonate and 3.0 Gy of X-irradiation.

Changes in generation of reactive oxygen species and antioxidant enzyme activities are associated with differentiation processes. The authors have studied the activity of superoxide dismutase (SOD) in sequentially cut stage-defined segments of rat seminiferous tubules. Great variation was observed in SOD activity along the seminiferous epithelial wave. At its highest, four-fold increases were observed in individual tubules. However, these changes showed no clear correlation to the stages of the cycle. To determine the effect of testosterone withdrawal, rats treated with ethane dimethanesulphonate (EDS) were studied. This treatment had no effect on the pattern of SOD activity along the seminiferous epithelial wave. Testes of other rats were exposed to local 3.0 Gy X-irradiation to cause selective loss of germ-cell populations. SOD activity in the seminiferous epithelium was not affected at 30 min or 7 d after X-irradiation. On day 31 post-irradiation, SOD activity increased at stages XIV-VI, peaking at stage III (P < 0.01 for comparison of stages XIV-VI with the other stages). The data presented here suggest that the activity of SOD in seminiferous epithelium is regulated over a wide range during spermatogenesis. Testosterone plays no major role in the control of seminiferous tubule SOD activity. The loss of spermatocytes and early spermatids by day 31 after X-irradiation revealed a stage-specific increase in SOD activity, which may be associated with the differentiation of elongated spermatids.

Dynamic Behavior of Salmonella‐Induced Membrane Tubules in Epithelial Cells

Salmonella Typhimurium is a facultative intracellular pathogen that causes acute gastroenteritis in man. Intracellular Salmonella survive and replicate within a modified phagosome known as the Salmonella-containing vacuole (SCV). The onset of intracellular replication is accompanied by the appearance of membrane tubules, called Salmonella-induced filaments (Sifs), extending from the SCV. Sifs are enriched in late endosomal/lysosomal membrane proteins such as lysosome-associated membrane protein 1, but their formation and ability to interact with endosomal compartments are not characterized. In this study, we use live cell imaging techniques to define the dynamics of Sif formation in infected epithelial cells. At early time-points, Sifs are simple tubules extending from the surface of SCVs. These tubules are highly dynamic and exhibit bidirectional, microtubule-dependent movement. At the distal ends of individual Sif tubules, furthest from the SCV, a distinct ‘leader’ domain was often observed. At later times, Sifs develop into highly complex tubular networks that extend throughout the cell and appear less dynamic than nascent Sifs; however, individual tubules continue to display bidirectional dynamics. Sifs can acquire endocytic content by fusion, indicating a sustained interaction with the endocytic pathway. Together, these results show that these Salmonella-induced tubules form a highly dynamic network that involves both microtubule-dependent motility and interactions with endosomal compartments.

Microscopic organization of the sperm storage tubules in the oviducal gland of the female gummy shark (Mustelus antarcticus), with observations on sperm distribution and storage

Oviducal gland morphology, the microscopic organization of the terminal zone, and sperm storage were described in the female gummy shark (Mustelus antarcticus). Mustelus antarcticus is a nonplacental viviparous hound shark, which displays minimal histotrophy during embryonic development. The animals examined represented all stages of maturity and gestation. The oviducal gland was found to have the same fundamental zonation as in most chondrichthyans. Using recent terminology, the oviducal gland of chondrichthyans has an anterior club zone, followed by a papillary zone, both of which produce jelly that surrounds the egg, a baffle zone that elaborates the tertiary egg envelope and a terminal zone, where sperm storage occurs. Each zone is composed of simple tubular glands that connect to transverse grooves, which extend the full width of the gland. The exception is the terminal zone, which does not have transverse grooves but consists of individual tubules. The microscopic organization and histochemical nature of the zones display similar patterns to those of other chondrichthyan genera. Tubules of the terminal zone contain four types of cell: ciliated cells, alcian blue-positive secretory cells, periodic acid-Schiff and alcian blue-negative secretory cells, and secretory columnar cells. These tubules end in recesses, the sperm storage tubules, which extend beyond the periphery of the baffle zone. Sperm were stored in the sperm storage tubules of all maturing and mature animals examined. Of note is the observation of stored sperm in an animal 1 year prior to first ovulation. Sperm were also observed throughout the uterine sphincter, body of the uterus, isthmus, and oviduct of maturing and mature animals, and in the uterine sphincter of an immature animal. These sperm represent immediately postcopulation aggregations of sperm and sperm in the process of migrating to the site of storage or to the site of fertilization.

Model of plasmon excitations in a bundle and a two-dimensional array of nanotubes

We calculate the plasma excitations in a bundle as well as a two-dimensional (2D) periodic array of aligned parallel multishell nanotubes on a substrate. The carbon nanotubes are oriented perpendicular to the substrate. The model we use for the system is an electron gas confined to the surface of an infinitely long cylinder embedded in a background dielectric medium. Electron tunneling between individual tubules is neglected. We include the Coulomb interaction between electrons on the same tubule and on different tubules for the same nanotube and neighboring nanotubes. We present a self-consistent field theory for the dispersion equation for intrasubband and intersubband plasmon excitations. For both the bundle and 2D array of aligned parallel nanotubes, the dispersion relation of the collective modes is determined by a three-dimensional wave vector with components in the direction of the nanotube axes and in the transverse directions. The dispersion equation is solved numerically for a single-wall nanotube 2D array as well as a bundle, and the plasmon excitation energies are obtained as a function of wave vector. The intertube Coulomb interaction couples plasmons with different angular momenta $m$ in individual nanotubes, lifting the $\ifmmode\pm\else\textpm\fi{}m$ degeneracy of the single-nanotube modes. This effect is analyzed numerically as a function of the separation between the tubules. We show that the translational symmetry of the lattice is maintained in the plasmon spectrum for the periodic array, and the plasmon energies have a periodic dependence on the transverse wave vector ${\mathbf{q}}_{\ensuremath{\perp}}$. For the bundle, the Coulomb interaction between nanotubes gives rise to optical plasmon excitations.

Study of spermatogenesis and thickening of lamina propria in the human seminiferous tubules

The negative correlation between the thickness of the lamina propria and Johnsen's score count in individual seminiferous tubules was observed and the tubules with thin lamina propria indicated almost complete spermatogenesis. It is suggested that the thin lamina propria may be one of the good indicators of complete spermatogenesis.