Giant Body Research Articles

Bone-bonding behavior of three heat-treated silica gels implanted in mature rabbit bone.

Silica gel has been reported to induce apatite nucleation on its surface in vitro and it can act as a stimulant that induces formation of chemical apatite (Ca-P) layers on the surfaces of bioactive glass-ceramics. In this study, apatite formation in response to and the bone-bonding behavior of silica gels implanted in the tibiae of mature rabbits were studied. Implants were made from three silica gels treated at 400, 800, and 1000 degrees C, and the effects of such heat treatment on the above parameters were investigated. The silica gel was made by hydrolysis and polycondensation of tetraethoxysilane in aqueous solution containing polyethylene glycol. Rectangular implants (15 mm x 10 mm x 2 mm) of each heat-treated silica gel were implanted into both tibial bones of mature male rabbits, which were killed 4 or 8 weeks after implantation, and the tibiae containing the implants were dissected out. The bone-implant interfaces were investigated using Giemsa surface staining, contact microradiography, scanning electron microscopy-electron probe microanalysis, and X-ray diffraction. Histologically, no bonding of bone to any of the silica gels was observed at any time postimplantation. Soft tissue was observed at the bone-silica gel interface, but there were no giant foreign body or inflammatory cells. A Ca-P-rich layer was observed only on small areas of the surfaces of the silica gels treated at 400 and 800 degrees C 4 and 8 weeks after implantation. X-ray diffraction analysis confirmed the presence of hydroxyapatite in these Ca-P-rich layers.(ABSTRACT TRUNCATED AT 250 WORDS)

Impact Erosion of Terrestrial Planetary Atmospheres

I review current ideas about the nature of the planetesimals - composition, size distribution, and the planetary encounter velocity. Previous papers on accretion and erosion of planetary atmospheres as a result of multiple impacts are reviewed. Finally, the effects of blowing off a substantial fraction of the atmosphere from a terrestrial planet due to a single giant body impact are discussed.

Impact Erosion of Terrestrial Planetary Atmospheres

I review current ideas about the nature of the planetesimals - composition, size distribution, and the planetary encounter velocity. Previous papers on accretion and erosion of planetary atmospheres as a result of multiple impacts are reviewed. Finally, the effects of blowing off a substantial fraction of the atmosphere from a terrestrial planet due to a single giant body impact are discussed.

Human-to-Rabbit Xenograft Model for Evaluation of Recanalization Techniques

The authors describe a xenograft model created by interposing human ath erosclerotic tissue into the rabbit aorta. Human atherosclerotic tissue obtained from either peripheral vascular operative specimens or from resected hearts of patients undergoing orthotopic cardiac transplantation were sectioned into 10 patches and 5 vessel segments and placed into the aortas of 15 rabbits. A thin platelet-fibrin layer adhered to the luminal surface of the graft but did not progress to occlude the graft. This layer matured over a two-week period, with ingrowth of fibroblasts. Endothelialization occurred only at the anastomotic sites. Rejection was characterized by development over a ten-day period of mul tinucleate giant foreign body cells and a dense inflammatory infiltrate advanc ing from the adventital surface. No necrosis of the xenograft was evident. This model is applicable to study the effects of balloon angioplasty, "hot tip" devices, mechanical atherectomy instruments, and various laser systems on human cal cific atherosclerotic vessels. Currently available animal atherosclerosis models do not provide a comparable test system.

Cytoplasmic intermediate filament proteins of invertebrates are closer to nuclear lamins than are vertebrate intermediate filament proteins; sequence characterization of two muscle proteins of a nematode.

The giant body muscle cells of the nematode Ascaris lumbricoides show a complex three dimensional array of intermediate filaments (IFs). They contain two proteins, A (71 kd) and B (63 kd), which we now show are able to form homopolymeric filaments in vitro. The complete amino acid sequence of B and 80% of A have been determined. A and B are two homologous proteins with a 55% sequence identity over the rod and tail domains. Sequence comparisons with the only other invertebrate IF protein currently known (Helix pomatia) and with vertebrate IF proteins show that along the coiled-coil rod domain, sequence principles rather than actual sequences are conserved in evolution. Noticeable exceptions are the consensus sequences at the ends of the rod, which probably play a direct role in IF assembly. Like the Helix IF protein the nematode proteins have six extra heptads in the coil 1b segment. These are characteristic of nuclear lamins from vertebrates and invertebrates and are not found in vertebrate IF proteins. Unexpectedly the enhanced homology between lamins and invertebrate IF proteins continues in the tail domains, which in vertebrate IF proteins totally diverge. The sequence alignment necessitates the introduction of a 15 residue deletion in the tail domain of all three invertebrate IF proteins. Its location coincides with the position of the karyophilic signal sequence, which dictates nuclear entry of the lamins. The results provide the first molecular support for the speculation that nuclear lamins and cytoplasmic IF proteins arose in eukaryotic evolution from a common lamin-like predecessor.

Does Newton's world model revive?

Newton's world model may have a physical meaning if the graviton has small non-zero mass and if the observable part of the Universe is the interior of a giant finite body. Both possibilities are in principle allowed.

Interactions between the Nucleus and Cytoplasmic Organelles during the Cell Cycle of Euglena gracilis in Synchronized Cultures III. Association between the Nucleus and Chloroplasts at an Early Stage in the Cell Cycle under Photoorganotrophic Conditions (Part II)1

Three-dimensional models of chloroplasts before and during their association with the nucleus in Euglena gracilis Z were constructed based on serial sections of cells taken during an early phase of the cell cycle in synchronized cultures under photoorganotrophic condition. Before association, the cell contained two to three chloroplasts which were composed of elongated tubular bodies extending in different directions toward the cell periphery. These tubular arms of chloroplasts were drawn toward the nucleus, and folded, with concurrent coalescence, into a single giant body surrounding the nucleus. A DAPI-fluorescence photomicrograph of a giant chloroplast revealed that the chloroplast-nucleoids were in the form of a continuous strand lying throughout the chloroplast body, and that some protuberances from the nucleoid strand were in especially close proximity to the nuclear periphery. A new mode of the chloroplast-nucleus connection was observed. The nucleus had conspicuous protrusions, whose distal ends were connected with the chloroplast. The outer membrane of the nuclear envelope was continuous with the outer chloroplast membrane, and at some sites, an open space was formed between the inner nuclear membrane and the inner chloroplast membrane.

Note on the age of the Giant Mascot ultramafic body, near Hope, B.C.

K/Ar ages from the Giant Mascot ultramafic body (119–95 m.y.) suggest that it is slightly older than adjacent diorite and tonalite (79–89 m.y.), which are shown to be members of the mid-Cretaceous Spuzzum Intrusions.

ELECTRON MICROSCOPE STUDY ON THE SPERMATOZOON OF THE LIPHISTIID SPIDER, HEPTATHELA KIMURAI

Intratesticular spermatozoa of Heptathela kirnurai have been examined with light and electron microscope. Living spermatozoon consists of a 20 to 25 μ-long spiral head and an approximately 6 μ-wide broad cytoplasmic portion. At the terminal end of the sperm head, there is a specialized acrosomal complex. The intact acrosome consists of an acrosomal vesicle, the lateroposterior side of which is deeply invaginated so that the whole vesicle forms a sheath around a slender acrosomal fiber. The acrosomal vesicle, except for the apical part of the vesicle, is filled with dense particulate material. Acrosomal fiber extends distally to form the spiral around the cork-screw nucleus. It is wrapped by a membranous sheath formed by an extension of the nuclear envelope. A single centriole is located in an invagination of the posterior end of the nucleus. A long flagellum coming from centriole coils 3 to 4 times around the periphery of the cytoplasmic region. Middle piece of the flagellum is enveloped by the mitochondrial sheath. In contrast to the conventional 9+2 pattern in cilia and flagella, the Heptathela sperm flagella have the 9+3 pattern, i.e. nine peripheral pairs plus three central tubules. Cytoplasmic region includes giant body, clusters of glycogen particles, lipids, and membranous structure.

Development and morphology of trachoma agent in the yolk sac cell as revealed by electron microscopy

The trachoma agent cultivated in the yolk sac of the chick embryo was examined by electron microscopy. A reticulated matrix is seen as a precursor of viral forms in the cytoplasm of the yolk sac cell 18 hours after inoculation. The matrix consists of fine filaments 100 A in width, which resemble chromosome fibrils. The matrix has no limiting membrane and no inner particles. In the next few hours the matrix is surrounded by a double membrane and forms a giant body (plaque by light microscopy) 1–5 μ in diameter. An inclusion cavity develops surrounding the giant body. The cavity is separated from the cytoplasm by a membrane. Forty-eight hours after inoculation large bodies (initial bodies by light microscopy) 0.5–1 μ in diameter predominate in the inclusion cavity. Each large body has a double outer membrane and a reticulated inner substance with slightly higher electron density than the giant body. Some internal structure is suggested in the reticulated substance. Seventy-two hours after inoculation elementary bodies 0.3–0.5 μ in diameter predominate. Each elementary body has a single membrane, a nucleoid, and a viroplasm. The nucleoid consists of coiled filaments 50 A in width which resemble DNA filaments in bacterial nucleoplasm. The mode of the development of the trachoma agent seems to be similar to viral replication. Elementary bodies seem to result from developmental forms by subdivision of the latter, but the subdivision seems to be different from bacterial binary fission.

THE FORMATION OF GIANT POLAR BODIES IN CENTRIFUGED EGGS OF ILYANASSA

1. If the second maturation spindle of the egg of Ilyanassa is displaced from the animal pole by centrifugal force, a giant polar body may be formed. If the sperm nucleus is included in the giant polar body the latter, instead of the egg proper, may develop.2. The close of the maturation division in centrifuged and elongated eggs is attended by the production of clusters of cytoplasmic lobes around the region where the achromatic figure lay. These lobes are distinct from the normal polar lobe.3. In strongly centrifuged eggs five zones of substances are separated. These include two clear zones separated by a band of fine, colorless granules.