Tubular Core Research Articles

Fine structure of human immunodeficiency virus (HIV) and immunolocalization of structural proteins

Ultrathin section and surface replica electron microscopy were applied in combination with immunoelectron microscopy to elucidate the fine structure of HIV. The shell of the tubular core shows p24 antigenicity, while p17 is located at the inner leaflet of the lipid membrane. The virus particle is studded with 70–80 protrusions. These knobs have a diameter of 15 nm, a height of 9 nm, and are probably arranged in a T = 7 I symmetry. The major envelope protein gpl20 is spontaneously shed from the viral surface. A possible role of released gpl20 in pathogenesis is discussed.

Structure of complex flagellar filaments in Rhizobium meliloti

The complex flagella of Rhizobium meliloti 2011 and MVII-1 were analyzed with regard to serology, fine structure, subunits, and amino acid composition. The serological identities of flagellar filaments of the two strains were demonstrated by double immunodiffusion with antiflagellin antiserum. The filaments had a diameter of 16 nm. Their morphology was dominated by the prominent undulations of an external three-start helix running at a 10-nm axial distance and at an angle of 32 degrees. Faint nearly axial striations indicated the presence of a tubular core of a different helical order. The complex filaments consisted of 40,000-dalton flagellin monomers. Typically, the amino acid composition was 3 to 4% higher in nonpolar residues and 5 to 7% lower in aspartic and glutamic acids (and their amides) than that of plain flagellar proteins. There were no immunochemical relationships among Pseudomonas rhodos, Rhizobium lupini, and R. meliloti complex flagella, suggesting that the latter represent a new class.

Intracisternal crystalline arrays of coated parallel tubules in cells of a human osteosarcoma.

Crystalline arrays of coated parallel tubules (CPT) were observed by electron microscopy within dilated cisternae of the rough endoplasmic reticulum of pleomorphic mononuclear cells in a human osteosarcoma. The wall of the peculiar intracisternal tubules consisted of an electron-dense thin membrane-like envelope which appeared to be composed of granular subunits. The electron-lucent tubular core together with the limiting envelope was approximately 15 nm in diameter. A coat of fuzzy material, approximately 10 nm thick, tightly surrounded the membrane-like wall of the tubules. Cross sections of accumulations of CPT showed the tubules to be arranged in a hexagonal crystalline array. The nature and significance of the intracisternal CPT are unknown.

The structure and composition of the love dart (gypsobelum) in Helix pomatia

The love dart of the snail Helix pomatia is a four-bladed, hollow spicule of calcium carbonate. The calcium carbonate is largely in the form of microcrystalline aragonite, the crystals being not more than 0.5 μm in size but assembled into sheets or blocks of much greater size. Protein occurs in the dart structure as an external sheath, as a lining to the tubular core and as a matrix component of the mineral phase Comparisons with the molluscan shell are drawn and a rationale for the architecture suggested.

Nuclear and cell division inSorodiplophrys stercorea, a labyrinthulid-like protist

Nuclear division in the labyrinthulid-like protist,Sorodiplophrys stercorea was studied and compared to the mitotic processes reported in other protistan forms.S. stercorea was found to have centrioles with nine peripheral singlet microtubules and a tubular core 300–400 A in diameter. The nuclear envelope remains intact throughout division, with microtubules passing through nuclear pores. The nucleolus disappears during nuclear division. After intranuclear division, cells cleave by introgressive cleavage while pronucleoli appear in the nuclei and fuse to form the single nucleolus characteristic of the interphase nucleus.

The Ulrastructure of the Spore of Nosema algerae (Protozoa, Microsporida), in Relation to the Hatching Mechanism of Microsporidian Spores

Summary: The spore of Nosema algerae from the tissues of Anopheles stephensi has a wall consisting principally of electron-dense exospore and electron-lucent endospore. The polar filament, composed of two membranes around an amorphous or tubular core, described eleven coils in the posterior half of the spore and joined anteriorly with the umbrella-shaped polar sac. The polaroplast consisted of close-packed single membranes and sacs disposed around the anterior straight part of the filament. There was no posterior vacuole. There were two nuclei in a central area of cytoplasm containing abundant ribosomes and cysternae of endoplasmic reticulum. The cytoplasm beneath the plasmalemma and around the coils of the polar filament lacked ribosomes. Various hypotheses for filament extrusion are discussed in the light of the present observations. It is proposed that the positions of the outer membranes of the polar filament are inverted during extrusion and that the core becomes a coat to the filament. Some of the cytoplasm, together with the nuclei, passes through the filament and probably acquires a membrane from the sealed tip of the filament to become the sporoplasm. The polaroplast does not participate structurally in extension of the filament.

The proboscis apparatus of the nemertineLineus ruber

The proboscis apparatus of the nemertineLinens ruberis divided into three segments: the anterior, middle and posterior proboscis, and in addition to these, the retractor muscle. The latter connects the caudal end of the posterior proboscis to the posterior dorsal wall of the rhynchocoel. The general arrangement of the constituent layers of the three segments of the proboscis is more or less similar: (1) inner epithelium, (2) basement membrane, (3) nerve plexus, and (4) one or two layers of muscle which are covered exteriorly by (5) basement membrane and (6) the endothelial cells. The endothelial cells are freely exposed to the rhynchocoel fluid. The inner epithelium of the anterior and posterior proboscis consists of only one type of lining cells, whereas the epithelium of the middle proboscis has many different types of cells, among which may be mentioned (1) ‘rhabdite’-forming cells, (2) ‘sensory’ cells, (3) cells with long microvilli, (4) mucussecreting cells, and (5) cells with acidophilic granules. The rhabdites of the rhabdite-forming cells are very characteristic. Two stages of the rhabdites have been seen: newly developed and mature rhabdites. In the former, the central tubular core of the structure is small and the ‘pool’ in which the rhabdite is embedded is large. In the mature rhabdite the reverse is true, i.e. the central tubular core is distended with electron-translucent secretion probably derived from the ‘pool’, since the latter is greatly reduced in size. The rhabdites are discharged in clusters into the lumen of the ‘resting’ proboscis and presumably over ‘prey’ when the proboscis is ejected. The muscles of the proboscis have ‘dual’ innervation. Aminergic and cholinergic nerve fibres, which arise from the dorsal cerebral ganglia, enter the proboscis at its anterior connexion (‘hinge’). In the aminergic nerve terminals two types of ‘synaptic vesicles’ have been resolved: vesicles of moderate density (20 to 50 nm) and dense-core vesicles (50 to 80 nm). Cholinergic terminals show typical vesicles of size 20 to 50 nm. The retractor muscle is apparently trebly innervated. ‘Synaptic contacts’ (mostly aminergic) occur at the junction of the proboscis and the retractor muscle. In addition, the retractor muscle has a probable peptidergic type of innervation. Neural terminals loaded with granules of size 140 nm, and thus comparable with other neurosecretory endings, are seen in the close vicinity of the retractor muscle. This histological evidence is supported by the observation that the muscle contracts vigorously when stimulated with oxytocin at a concentration of 0.01 unit/ml. The fluid relationships between the rhynchocoel and the vascular system, that allow the proboscis to be freely ejected and withdrawn, are discussed.

Morphology and developmental stages of Gomphrena virus

A virus inducing local lesions on globe amaranth has been named Gomphrena virus (GV) and was verified as closely related or identical to the lettuce necrotic yellows virus reported in Australia. Negatively stained dip preparations from plants infected with GV, revealed bacilliform particles. These, considered as GV particles, have a relatively complex structure, measuring 220–260 mμ in length and 80–100 mμ in diameter. They have an outer membrane, 8–10 mμ thick, provided with evenly spaced beadlike projections about 6–7 mμ long. Enveloped by this outer coat there is an inner tubular core, 200–240 mμ long and 60–70 mμ in diameter, with an axial channel 35–40 mμ wide, and exhibiting about 80–90 alternate light and dark cross bands, each 2.6 mμ wide. This inner core is interpreted as the virus nucleoeapsid. Examination of sections of osmium- and permanganate-fixed, Epon-embedded, tissues from infected plants under the light microscope, revealed inclusions, apparently intranuclear. These inclusions, when viewed in the electron microscope, were shown to consist of large numbers of particles, morphologically similar to those seen in dip preparations, usually arranged in two- or three-dimensional crystalline array within the membranes of the nuclear envelope. Sporadically, particles were also found within elements of the endoplasmic reticulum. Cells infected with GV usually showed some changes, the most conspicuous appearing in the nucleus, in which there was a reduction or disappearance of chromatic material and an abnormal increase in the size of the nucleolus, which usually was vacuolated. Frequently, tubular particles oriented at random and similar to the inner core of the GV particles, but with variable length, were found in the nuclear matrix or inside the nucleolar vacuoles. They also sometimes appeared in crystalline array or apparently being protruded from the nucleolus. Also what was interpreted as intermediary stages in the maturation process of GV particles were observed. In these, the tubular particles are enveloped by the inner membrane of the nuclear envelope, which buds toward the perinuclear space. It is pointed out that GV and other plant viruses provided with an outer envelope, constitute a new group in addition to the well known spherical and elongated plant viruses.

Instruments and Methods: Portable Thermal Core Drill for Temperate Glaciers

AbstractIn the summer of 1962 a completely portable and relatively simple electrically heated thermal core drill of new design was constructed and used to obtain 16 oriented samples of ice 2.5 cm. in diameter by 120 cm. in length from depths ranging from 12 m. to 137 m. in lower Blue Glacier, Mount Olympus, Washington, U.S.A. The thermal element is a 0.260-in. (0.66-cm.) diameter 300-W. 150-V. tubular heater bent to form an annulus with an external diameter of 5.0 cm. Opposed ratchet-like teeth break off and hold the core inside the tubular core barrel. Orientation is recorded photographically by a commercial inclinometer modified to show azimuth and to be controlled from the surface.

Instruments and Methods: Portable Thermal Core Drill for Temperate Glaciers

AbstractIn the summer of 1962 a completely portable and relatively simple electrically heated thermal core drill of new design was constructed and used to obtain 16 oriented samples of ice 2.5 cm. in diameter by 120 cm. in length from depths ranging from 12 m. to 137 m. in lower Blue Glacier, Mount Olympus, Washington, U.S.A. The thermal element is a 0.260-in. (0.66-cm.) diameter 300-W. 150-V. tubular heater bent to form an annulus with an external diameter of 5.0 cm. Opposed ratchet-like teeth break off and hold the core inside the tubular core barrel. Orientation is recorded photographically by a commercial inclinometer modified to show azimuth and to be controlled from the surface.