Tail-like Structure Research Articles

A new type of first-order phase transition in ferroelectric thin films

Phase transition behaviour in ferroelectric thin films is studied via the calculation of free energy for the case when the bulk phase transition is second order. If the spontaneous polarization is reduced near the surface, the phase transition in ferroelectric thin films will become of first order. As well as shifts in the Curie point to a lower temperature, the peak height of susceptibility at the critical point decreases with decrease in the film thickness. When the spontaneous polarization is enhanced near the surface, the phase transition behaviour of spontaneous polarization shows a tail-like structure.

Maturation of the External Urinary Sphincter: A comparative Histotopographic Study in Humans

The developmental anatomy of the striated urinary sphincter remains controversial and is scantly documented in children. We compared its structure and configuration in the fetus, infant and adult to determine anatomical differences among these groups. We removed 25 postmortem specimens from fetuses, infants and children, which were fixed and stained for histological study. Ages ranged from 14 weeks of gestation to 12 years postpartum. Transverse and mid sagittal sections were obtained from the bladder neck to the membranous urethra in male and the whole urethra in female subjects. At the level of the membranous urethra in male and mid urethra in female subjects the striated muscle fibers completely encircle the urethra and join behind it to form a tail-like structure that runs posteriorly towards the perineal body. This structure is mid sagittal in male and mediolateral in female subjects. At 3 to 4 months of life, at the level of the bulbourethral glands the tail disappears; the striated sphincter becomes horseshoe-shaped and its 2 branches bifurcate posteriorly to envelop these glands. The urethral striated sphincter consists of scantly dispersed muscle fibers in the fetus. In young infants it becomes well defined in both sexes with the presence of a tail-like structure that characterizes this age group. In older subjects this tail disappears and the sphincter assumes a horseshoe or omega-shaped configuration as splitting of the sphincter progresses caudo-cranially with development. We attempt to determine whether the ring configuration of the voluntary sphincter contributes to high voiding pressures that are reported to occur in some newborns and infants.

The structure and length of tail-associated phenomena in the solar wind downstream from the Earth

The length of the geomagnetic tail, estimated on the basis of the open model of the magnetosphere, is generally taken to be ∼ 1000 R E. Here we show that a tail-like structure consisting of field lines disconnected from the Earth and lying downstream from the tail reconnection region will typically remain present up to distances of ∼ 5000 R E. At even larger distances, the most prominent terrestrial effect is expected to be substorm-associated plasmoids propagating in the solar wind.

2-dimensional observation of recorded magnetization transitions in perpendicular recording

Two-dimensional magnetic transition shapes written in a perpendicular recording medium were studied using a large-scale model which simulates a system consisting of a single-pole head and a double-layer medium. The magnetization distribution shapes are calculated from the measured stray field distribution on the surface of the recording medium. The authors describe the experimental method and the results derived for a large-scale medium. They observed a tail-like structure at the corner of the track and transition edges along the track, which can be interpreted as the effect of the demagnetization field from the DC-erased magnetization. The shape of the track edge is similar to that of the transition edge, which suggests that perpendicular recording is suitable for narrow-track recording. >

Spermatogenesis in a nematode Nippostrongylus brasiliensis

The structure and development of the spermatozoon of Nippostrongylus brasiliensis was studied with the electron microscope using thinsectioned material and tissue prepared by the freeze-fracture technique. The developing germ cells are connected via a complex anucleate rachis which begins as fine threads of cytoplasm joining the spermatogonia. It rapidly enlarges to a broad, central core which not only anchors and joins the spermatocytes, but also appears to be an important site for protein synthesis. Formation of membranous organelies (MOs) from RER-associated Golgi bodies dominates the activities of the growing spermatocytes. As the latter approach meiosis, the rachis declines in importance and finally becomes the site of breakdown of the residual cytoplasm. The spermatid chromatin condenses into a long cylinder during spermatogensis. A pair of centrioles in an indentation at the anterior end are believed to organize long microtubules which are responsible for moving the nucleus through then out of the sperm cytoplasm to form a tail-like structure. Thus the cytoplasmic region of mature sperm contains only mitochondria and MOs; a small part of the anterior is amoeboid.

Structure and development of the spermatozoon of the parasitic nematode, Nematospiroides dubius

Spermatogenesis and sperm maturation in Nematospiroides dubius were studied using electron microscopy. The testis is telegonic and germ cells in the zones of mitosis, growth and meiosis are connected by a central anucleate mass of cytoplasm, the rachis. The early part of spermatogenesis is dominated by the synthesis and growth of membrane-bound vesicles called membranous organelles, which originate from RER-associated Golgi bodies. Following meiosis the spermatids separate from the rachis and their chroinatin, which is no longer bounded by a nuclear envelope, condenses into an arrow-head shape and is extruded to form a tail-like structure. After insemination spermatozoa undergo a profound change called activation. The cytoplasmic region which was previously long and cylindrical becomes spherical and the membranous organelles which lined its perimeter fuse with the plasma membrane and become confined to the posterior hemisphere of the sperm, close to the nuclear tail. The anterior half of the sperm is devoid of organelles but contains many filaments organized into clumps and chains; this region being responsible for amoeboid locomotion of the sperm.

Cutaneous signs of spinal dysraphism. Report of a patient with a tail-like lipoma and review of 200 cases in the literature

The term "spinal dysraphism" was coined in 1940 by Dr Lichtenstein to designate incomplete fusion or malformations of structures in the dorsal midline of the back, particularly congenital abnormalities of the vertebral column and spinal cord. Raphes develop on the face and head, brancheal arches, sternum, and spinal column. When dysraphism occurs in these sites, failure of closure of fontanelles, cleft lip and palate, brancheal cysts, and abnormalities of the ribs and spine result. A review of 200 cases of occult spinal dysraphism showed the condition to be more common in female patient and to be associated with cutaneous signs in more than 50% of instances. The age at which neurologic symptoms appeared in recorded cases is from birth to 76 years, the average being three years. A case of spinal dysraphism with a tail-like cutaneous structure is presented. The cutaneous manifestations accompanying spinal dysraphism that may lead to early recognition of this syndrome and early institution of treatment are discussed.

Cutaneous Signs of Spinal Dysraphism

• The term "spinal dysraphism" was coined in 1940 by Dr Lichtenstein to designate incomplete fusion or malformations of structures in the dorsal midline of the back, particularly congenital abnormalities of the vertebral column and spinal cord. Raphes develop on the face and head, brancheal arches, sternum, and spinal column. When dysraphism occurs in these sites, failure of closure of fontanelles, cleft lip and palate, brancheal cysts, and abnormalities of the ribs and spine result. A review of 200 cases of occult spinal dysraphism showed the condition to be more common in female patients and to be associated with cutaneous signs in more than 50% of instances. The age at which neurologic symptoms appeared in recorded cases is from birth to 76 years, the average being three years. A case of spinal dysraphism with a tail-like cutaneous structure is presented. The cutaneous manifestations accompanying spinal dysraphism that may lead to early recognition of this syndrome and early institution of treatment are discussed. (<i>Arch Dermatol</i>114:573-577, 1978)

Explorer 45 (S³-A) observations of the magnetosphere and magnetopause during the August 4-6, 1972, magnetic storm period

The Explorer 45 (S³-A) satellite performed extensive field and particle measurements in the heart of the magnetosphere during the double magnetic storm period of August 4–6, 1972. Both the ground level magnetic records and the magnetic field deformations measured along the orbit by the satellite indicated the existence of only a moderate ring current. This was confirmed by the measurements of the total proton energy density by the on-board particle detectors, which showed a maximum energy density less than the densities observed during the December 1971 and June 1972 magnetic storms. The plasmapause in the noon quadrant was eroded continuously from the onset of the first storm at the beginning of August 4 to an altitude below L = 2.07 at about 1800 hours on August 5. Throughout the entire orbit during which the second sudden commencement occurred a large amount of low-frequency electric and magnetic field noise was encountered. The most remarkable observation during this orbit was the contraction of the magnetopause to distances inside the satellite location at L = 5.2. The magnetic field reversed direction and increased in magnitude to more than 500 γ, the particle detectors encountered huge fluxes of streaming protons, and the field detectors measured intense broad band noise. Following the period of magnetospheric boundary crossings, Explorer 45 encountered a series of large-amplitude magnetospheric oscillations, seen both in the dc and low-frequency field measurements and in the intensities of the particle fluxes. As is true for other storms, a region of detached plasma or a taillike structure was encountered in the dusk hours during the development of the second main phase, and a nose structure in the proton ring current distribution was observed, which has been shown to be a characteristic feature in the dusk hours during the ring current development.

Purification and properties of boticin P produced by Clostridium botulinum.

A bacteriocin produced spontaneously by a nontoxigenic strain of Clostridium botulinum, type E, PM-15, has been isolated and designated boticin P. It was purified by ammonium sulfate precipitation, gel filtration on Sephadex G-100, sucrose density gradient centrifugation, and cesium chloride equilibrium density gradient centrifugation. Boticin P is composed mainly of proteins (98.8%) with a trace amount of carbohydrates (0.4%), and has an apparent molecular weight in excess of 4 × 106 daltons as estimated by gel filtration on Sepharose 2B. Electron microscopic examination of boticin P reveals a phage tail-like structure of 100 nm in length.Boticin P exerted a static effect on vegetative growth and spore outgrowth but not on the initial events of germination. The boticin was active on 10/12 toxigenic and 3/6 nontoxigenic type E and 2/2 nonproteolytic type B strains of C. botulinum. The activity spectrum on 27 strains supports the proposal that type E and the nonproteolytic type B strains belong to the same taxosubspecies.

Experimental test of magnetospheric models

The barium cloud injection deep into the magnetosphere of Sept. 21, 1971, has revealed that the quiet-time near-equatorial nightside magnetic field is significantly different from that predicted by existing quite-time models. The influence of currents flowing on or near the geomagnetic equator gives the field a more tail-like structure at a distance as close as 5 earth radii. Several models have been tried out to obtain a best fit to the experimental observations of the shape of the field-aligned ion cloud. Although this method does not lead to a unique solution, the most acceptable option emerging from this analysis is a quiet-time tilted image-dipole model with a Williams-Mead tail field and a disclike ring current on the geomagnetic equator.

Ultrastructural studies of the envelopment and release of guinea pig herpes-like virus in cultured cells

The process of envelopment and release of guinea pig herpes-like virus was examined in both infected guinea pig kidney and thymus tissue culture cells by electron microscopy. The majority of the nucleocapsids were enveloped by budding into nuclear vacuoles; some were enveloped by budding from the inner nuclear membrane. Budding into cytoplasmic vacuoles was also seen. Many enveloped virus particles inside the nuclear vacuoles were pear shaped with a tail-like structure. Approximately 23% of pear-shaped virus particles were seen in the infected thymus fibroblastic cells, but only 6% were found in the infected epithelial cells. The envelopes of all nuclear enveloped virus particles appeared as smooth membranes, while the majority of particles exhibiting fuzzy and thick dense envelopes were seen in the cytoplasm or extracellular space. The average diameter of the cytoplasmic or extracellular enveloped virus particles was approximately 167 nm, and the average diameter of the nuclear enveloped virus particles was about 146 nm. Data also showed that mature nuclear virus particles were first released into perinuclear cisterna and then traveled through cytoplasmic channels to the extracellular space.

Studies on temperate phages of Lactobacillus salivarius. I. Morphological, biological, and serological properties of newly isolated temperate phages of Lactobacillus salivarius.

Twenty-three temperate phages of Lactobacillus salivarius isolated from human feces were studied as to their morphological, biological, and serological properties. (1) Among 30 strains of L. salivarius tested, 23 strains were lysed by induction with mitomycin C (MC). In all these lysates, phage particles were detected by electron microscopic examination. (2) These phages were morphologically divided into three groups: particles with a regular hexagonal head and a long flexible tail; particles having a regular hexagonal head with or without a short tail-like structure; particles with an elongated head and a long noncontractile tail. (3) Only two, phage 223 having an elongated head and phage 227 with a regular hexagonal head and a long noncontractile tail, produced tiny and very turbid plaques on several host bacteria. Six phages could produce only inhibition zones, ranging from complete inhibition through partial inhibition to normal growth by a serial dilution spot test. (4) All these killer particles could also inhibit the growth of their producer cells. (5) A serological relationship was observed between temperate phages and killer particles, and this was somewhat consistent with the morphological groupings.

The structure and development of the spermatozoon of Aspiculuris tetraptera (Nematoda).

ABSTRACT The mature spermatozoon of Aspiculuris tetraptera has a distinct head-like structure and a tail-like structure. The tail contains a long mitochondrion which extends from within the head almost to the posterior end of the tail. Two bundles of microtubules oriented parallel to the longitudinal axis also extend the length of the tail on either side of the mitochondrion. The head of the spermatozoon contains abundant cytoplasm but no nucleus. The DNA of the spermatozoon is in the tail-like structure where it is associated with an electron-dense sheath and the two bundles of microtubules. The head can put out pseudopodia and it is suggested that they may be involved in locomotion or may be acrosome-like. The tail, which structurally resembles a motile appendage, has not been seen to move. This spermatozoon differs markedly in its structure from all others which have been described.

Electron microscope study of the Graffi virus in the bone marrow of leukemic mice

Bone marrow from C57BL mice with myeloid leukemia induced by Graffi virus has been studied with the electron microscope by ultrathin section and negative stain techniques. Virus particles were usually found in different types of bone marrow cells as well as in extracellular spaces. However, the highest number of particles in various stages of maturation was observed in the cytoplasm of megakaryocytes. Two main types of virus particle were found: the immature Al particle and the mature C particle. They were morphologically indistinguishable from other murine leukemogenic viruses. In partially purified preparations studied by negative staining, some of the particles which were not penetrated by PTA, frequently showed a tail-like structure of variable length. In ultrathin sections, particles were found to originate by budding from the cell membranes. Budding of particles was particularly evident in megakaryocytes and especially within the granules and cytoplasmic vesicles or in connection with the platelet demarcating membranes. The findings of a high number of virus particles in all stages of maturation in megakaryocytes together with a certain degree of megakaryocytosis observed in the bone marrow suggest that this type of cell is possibly one of the main source of production of the virus. A few particles resembling morphologically mycoplasma were detected within the cytoplasm of some immature bone marrow cells.