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At least 811 records · Page 45Linked to original sources
PubMed2004

Reconstituted type V collagen fibrils as cementing materials in the formation of cell clumps in culture.

Previous studies have reported that type V collagen is an anti-adhesive substrate for cultured cells in that the cells detach from culture dishes coated with type V collagen molecules or polypeptides derived from them. We have noticed that human fetal lung fibroblasts (TIG-1) initially show no reduction in adherence to and spreading on a dish coated with reconstituted type V collagen fibrils but eventually detach from the dish and form cell clumps. To determine the way in which reconstituted type V collagen fibrils are involved in cell clump formation, we have followed the fate of the fluorescence of type V collagen fibrils pre-labeled with fluorescein isothiocyanate. Essentially, all the fluorescence disappeared from the dish surface as the cells detached and was condensed in the cell clumps. The cells that were recovered from clumps and dissociated into separate cells by trypsin treatment proliferated normally after they were seeded on a bare culture dish. This result and those from gel electrophoresis, fluorescence microscopy, and a cell proliferation assay indicate that the cell detachment from the dish is not caused by cell necrosis or apoptosis but by cellular motility together with the unique features of type V collagen fibrils. Not only the adherence of type V collagen fibrils to TIG-1 cells is much stronger than that to the culture dish, but the fibrils are retained on the cellular surface. The strong adherence of type V collagen fibrils to cells plays a role in cementing TIG-1 cells together.

Cell Adhesion↗
PubMed2003

Application of composted urban residue enhanced the performance of afforested shrub species in a degraded semiarid land.

Improvement of physical-chemical soil quality is a key step for carrying out revegetation programs of degraded lands in Mediterranean semiarid areas. Organic residue addition may restore the quality of these areas. A field experiment was conducted in a silt-loam soil (Typic Petrocalcid) from a degraded semiarid Mediterranean area to evaluate the effect of the addition of a composted urban residue on soil aggregate stability, bulk density and chemical properties and on the establishment of Pistacia lentiscus and Retama sphaerocarpa seedlings. The composted residue was applied at a rate of 6.7 kg m(-2) before planting. The nutrient content (NPK), total organic C and water soluble C were increased and bulk density was decreased, in the rhizosphere soil of both shrub species, by the composted residue. The addition of composted residue significantly increased the soil aggregate stability by about 22% for both shrub species. The beneficial effect of the composted residue on soil quality still persisted 18 months after addition. Eighteen months after planting, the addition of composted residue to soil had increased significantly the production of shoot biomass by P. lentiscus and R. sphaerocarpa, by about 160% and 320% respectively, compared to control values. Composted residue addition to soil can be considered an effective preparation method of a degraded area for carrying out successful revegetation programs with Mediterranean shrubs under semiarid conditions.

Conservation of Natural Resources↗
PubMed1974

Amylases from aleurone layers and starchy endosperm of barley seeds.

Amylases from incubated aleurone layers or from starchy endosperm of barley seeds (Hordeum vulgare L. cv. Himalaya) were investigated using acrylamide gel electrophoresis and analytical gel filtration with Sephadex G-200. Electrophoresis of amylase from aleurone layers yields seven visually distinct isozymes with an estimated molecular weight of 43,000. Because each isozyme hydrolyzes beta-limit dextrin azure and incorporates calcium-45, they are alpha-amylases. On Sephadex G-200, amylase from the aleurone layers is separated into seven fractions ranging in estimated molecular weights from 45,000 to 3,000. Little or no activity is observed when six fractions are subjected to electrophoresis. Electrophoresis of only the fraction with the estimated molecular weight of 45,000 gave the seven isozymes. The amylases are heat labile and cannot be stabilized by the presence of substrate or by the protease inhibitor, phenylmethylsulfonylfluoride. Electrophoresis of amylase from the starchy endosperm yields nine beta-amylases. Four of these beta-amylases are isozymes with an estimated molecular weight of 43,000. The other five forms of beta-amylase represent molecular aggregates of the four basic beta-amylase monomers. A dimer, a tetramer, and an octamer of beta-amylase can be identified with estimated molecular weights of about 86,000, 180,000 and 400,000, respectively. These estimated molecular weights were confirmed on Sephadex G-200. There are five additional fractions of beta-amylase with estimated molecular weights ranging from 30,000 to 4,000. These fractions are not observed electrophoretically.

Journal Article↗
PubMed2000

Clonal variation in morphology, growth, physiology, anatomy and ultrastructure of container-grown white spruce somatic plants.

We assessed clonal variation in morphological variables, mineral nutrition, root growth capacity, net photosynthesis, tannin distribution, and cuticle and epicuticular wax features within four families of white spruce (Picea glauca (Moench) Voss). Seeds were collected from four families obtained through controlled crosses among selected genotypes. For each family, plants were produced either from seeds (zygotic) or by somatic embryogenesis (clones). Each family was therefore represented by its zygotic seedlings and three clones. Within a family and under similar growth conditions, several clones differed significantly from the zygotic seedlings in height, root-collar diameter, needle dry mass, branch density, shoot dry mass, root dry mass, and length of needles. Branch density (number of first-order branches per cm height) of zygotic seedlings and clones varied from 0.8 to 1.4 branches cm(-1) and from 0.6 to 1.3 branches cm(-1), respectively. Mean needle length of zygotic seedlings and clones ranged from 11 to 14 mm and from 11 to 17 mm, respectively. For many variables (height, dry mass of new roots, needle dry mass and branch density), differences among clones were significantly greater than differences among zygotic seedlings within a family. Tannins were more abundant in needles of clones than in needles of zygotic seedlings. In some clones, tannins occurred as a ribbon along the central vacuole, whereas in others they appeared as aggregates dispersed in the vacuole. Within a family, N, P and K showed considerable variations in their use efficiency. Interclonal variations were observed in root growth potential and net photosynthesis. Variations in growth and physiology reflect genetically determined differences among clones within a family.

Genetic Variation↗
PubMed1975

Expression of differentiated activities in reaggregated brain cell cultures.

Dissociated fetal mouse brain cells are allowed to reassociate in rotation culture to form aggregates. After several weeks these reaggregated brain cell cultures show markedly increased specific activities of monoamine oxidase, lactate dehydrogenase, and the brain-specific protein S-100, while catechol-O-methyltransferase activity increases slightly. Similar changes in these activities are found during mouse brain maturation. The amounts of monoamine oxidase, catechol-O-methyltransferase, and S-100 were also determined in surface cultures of fetal mouse brain cells, as well as glioma and neuroblastoma cell lines. The fetal brain and glial cell cultures possess much higher activities than the cultured neuroblastoma cells. However, lactate dehydrogenase activity was highest in the glioma and lowest in the surface cultures of fetal brain cells.

Age Factors↗
PubMed2005

Resveratrol, a phenolic antioxidant with effects on blood platelet functions.

The main purpose of this article is to provide an overview of the currently available evidence of antiplatelet properties of resveratrol (3,4('),5-trihydroxystilbene). Resveratrol, a phenolic compound found naturally in fruits, nuts, flowers, seeds and bark of different plants is integral part of human diet. It exhibits a wide range of biological effects, including antiplatelet, anti-inflammatory, anticancer, antimutagenic and antifungal properties. It is also a potent antioxidant, reactive oxygen species scavenger and metal chelators. Resveratrol reduces lipid peroxidation, oxidation and nitration of platelet and plasma proteins. This review article describes the chemical structure of resveratrol, its biological activity, the effects on blood platelet functions and the mechanisms involved in its action on blood platelets, the cells which play an important role not only in the haemostatic process, but also in pathogenesis of cardiovascular diseases.

Animals↗
PubMed1992

Sequence requirements for induction of cytolysis by the T cell antigen/Fc receptor zeta chain.

The zeta chain of the T cell antigen receptor is a dimeric transmembrane protein with a very short extracellular domain and an extended cytoplasmic tail that triggers T cell effector function when aggregated by extracellular stimuli. We have reduced the active site of zeta to an 18 residue motif that can be appended to the intracellular domain of other transmembrane proteins to endow them with receptor-like activity. The compact size of the motif appears to eliminate zeta mechanisms based on enzymatic activity and suggests that one or at most a few cellular proteins interact with the zeta intracellular domain to initiate signal transduction. Analysis of individual amino acids within the 18 residue element reveals two phylogenetically conserved tyrosines that are absolutely required for activity and other residues that are less essential but contribute to the efficacy of receptor-directed cytolysis.

Amino Acid Sequence↗
PubMed2002

Study on the three-dimensional proliferation of rabbit articular cartilage-derived chondrocytes on polyhydroxyalkanoate scaffolds.

Polymer scaffold systems consisting of poly(hydroxybutyrate-co-hydroxyhexanoate) (PHBHHx)/polyhydroxybutyrate (PHB) (PHBHHx/PHB) were investigated for possible application as a matrix for the three-dimensional growth of chondrocyte culture. Blend polymers of PHBHHx/PHB were fabricated into three-dimensional porous scaffolds by the salt-leaching method. Chondrocytes isolated from rabbit articular cartilage (RAC) were seeded on the scaffolds and incubated over 28 days, with change of the culture medium every 4 days. PHB scaffold was taken as a control. Methylthiazol tetrazolium (MTT) (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltertra-zolium bromide) assay was used to quantitatively examine the proliferation of chondrocytes. Results showed that chondrocytes proliferated better on the PHBHHx/PHB scaffolds than on PHB one. The maximal cell densities were all observed after 7 days of incubation. As for the blend polymers, cells grew better on scaffolds consisting of PHBHHx/PHB in ratios of 2:1 and 1:2 than they did on PHBHHx/PHB of 1:1. Scanning electron microscopy (SEM) also showed that large quantities of chondrocytes grew initially on the surface of the scaffold. After 7 days, they further grew into the open pores of the blend polymer scaffolds. Morphologically, cells found on the surface of the scaffold exhibited a flat appearance and slowly form confluent cell multilayers starting from 14 to 28 days of the growth. In contrast, cells showed rounded morphology, formed aggregates and islets inside the scaffolds. In addition, chondrocytes proliferated on the scaffold and preserved their phenotype for up to 28 days.

Animals↗
PubMed1997

Aortic endothelial cells regulate proliferation of human monocytes in vitro via a mechanism synergistic with macrophage colony-stimulating factor. Convergence at the cyclin E/p27(Kip1) regulatory checkpoint.

Monocyte-derived macrophages (Mphis) are pivotal participants in the pathogenesis of atherosclerosis. Evidence from both animal and human plaques indicates that local proliferation may contribute to accumulation of lesion Mphis, and the major Mphi growth factor, macrophage colony stimulating factor (MCSF), is present in atherosclerotic plaques. However, most in vitro studies have failed to demonstrate that human monocytes/Mphis possess significant proliferative capacity. We now report that, although human monocytes cultured in isolation showed only limited MCSF-induced proliferation, monocytes cocultured with aortic endothelial cells at identical MCSF concentrations underwent enhanced (up to 40-fold) and prolonged (21 d) proliferation. In contrast with monocytes in isolation, this was optimal at low seeding densities, required endothelial cell contact, and could not be reproduced by coculture with smooth muscle cells. Intimal Mphi isolated from human aortas likewise showed endothelial cell contact-dependent, MCSF-induced proliferation. Consistent with a two-signal mechanism governing Mphi proliferation, the cell cycle regulatory protein, cyclin E, was rapidly upregulated by endothelial cell contact in an MCSFindependent fashion, but MCSF was required for successful downregulation of the cell cycle inhibitory protein p27(Kip1) before cell cycling. Thus endothelial cells and MCSF differentially and synergistically regulate two Mphi genes critical for progression through the cell cycle.

Adolescent↗
PubMed1991

Correlated Si isotope anomalies and large 13C enrichments in a family of exotic SiC grains.

A suite of morphologically distinctive silicon carbide (SiC) grains from the Orgueil and Murchison carbonaceous chondrite meteorites contains Si and C of highly anomalous isotopic composition. All of the SiC grains in this suite are characterized by a distinctive platy morphology and roughly developed hexagonal crystal forms that allow them to be distinguished from other types of SiC found in the host meteorites. The delta 29Si and delta 30Si values of individual SiC crystals deviate from those of normal solar material by more than 100%, while the delta 13C values range from 150 to 5200%. Isotopically normal C and Si are not found in any of these SiC crystals. The SiC grains belonging to this morphological suite are isotopically distinct from fine-grained SiC aggregates and other morphological types of SiC in unequilibrated meteorites. The 29Si/28Si and 30Si/28Si ratios of these platy grains are well correlated and define a linear array that does not pass through the composition of normal, solar Si. This behavior contrasts sharply with the diverse and poorly correlated Si isotopic compositions shown by the total SiC population. We suggest that the distinctive morphological characteristics and comparatively simple Si isotope systematics identify the platy SiC crystals as a genetically related family, formed around a single, isotopically heterogeneous presolar star or an association of related stars. The enrichments in 13C and the Si isotope systematics of the platy SiC are broadly consistent with theoretical models of nucleosynthesis in low-mass, carbon stars on the asymptotic giant branch. The Si isotope array most plausibly reflects mixing between 28Si-rich material, inherited from a previous generation of stars, and material enriched in 29Si and 30Si, produced in intershell regions by neutron capture during He-burning. 13C is also produced in intershell regions by proton reactions on 12C seed nuclei and is carried with s-process nuclei to the stellar envelope by convection which penetrates down to the He shell. The absence of a correlation between the Si and C isotopic compositions of the SiC suggests either episodic condensation of SiC, extending over several thermal pulses, in the atmosphere of a single star, or derivation of the SiC from several stars characterized by different rates of 13C production. In the multiple star scenario, the linear correlation of the 29Si/28Si and 30Si/28Si ratios among the platy SiC indicates that these stars evolved from a common Si seed composition under similar conditions of neutron-capture nucleosynthesis. The 29Si/30Si ratio of the SiC, inferred by us to be produced by neutron capture in the stellar interior, is distinct from values calculated from models of nucleosynthesis in AGB stars.

Astronomical Phenomena↗
PubMed1996

Conditions which promote mineralization at the bone-implant interface: a model in vitro study.

This in vitro study was an investigation of osteoblast functions on glass substrates modified with the bioactive peptide Arg-Gly-Asp-Ser (RGDS) in the absence and presence of recombinant human Osteogenic Protein-1 (OP-1); control substrates were plain glass, glass modified with amine groups, and glass modified with the non-adhesive peptide Arg-Asp-Gly-Ser. In serum-free cell culture medium, osteoblasts adhered in greater numbers (P < 0.1) to glass modified with RGDS, compared to adhesion on all other substrate types tested in the present study. In the presence of serum proteins, osteoblasts adhered similarly to all substrate types examined, in the absence or presence of 100 ng ml-1 OP-1. The presence of 100 ng ml-1 OP-1 inhibited (P < 0.1) 72 h proliferation of sparsely seeded (2500 cells cm-2) cultures on all substrates examined in the present study. OP-1 (100 ng ml-1) promoted 21 day mineralization on all substrates examined; in addition, mineralization was further enhanced in osteoblast cultures grown on glass modified with the adhesive peptide RGDS. The present study establishes conditions which can be utilized in the design of dental/orthopaedic biomaterials which elicit timely, specific responses from surrounding bone tissue.

Amino Acid Sequence↗
PubMed1999

Blockade of GpIIb/IIIa inhibits the release of vascular endothelial growth factor (VEGF) from tumor cell-activated platelets and experimental metastasis.

Evidence that platelets play a role in tumor metastasis includes the observation of circulating tumor cell-platelet aggregates and the anti-metastatic effect of thrombocytopenia and anti-platelet drugs. Platelets have recently been shown to contain vascular endothelial growth factor (VEGF) which is released during clotting. We therefore studied the effects of (1) tumor cell-platelet adherence and tumor cell TF activity on platelet VEGF release; and (2) the effects of GpIIb/IIIa blockade on tumor cell-induced platelet VEGF release, tumor cell-induced thrombocytopenia and experimental metastasis. Adherent A375 human melanoma cells (TF+) and KG1 myeloid leukemia (TF-) cells were cultured in RPMI containing 10% fetal bovine serum. Platelet-rich plasma was obtained from normal citrated whole blood and the presence of VEGF (34 and 44 kDa isoforms) confirmed by immunoblotting. Platelet-rich plasma with or without anti-GpIIb/IIIa (Abciximab) was added to A375 monolayers and supernatant VEGF measured by ELISA. Tumor cell-induced platelet activation and release were determined by CD62P expression and serotonin release respectively. In vitro, tumor cell-platelet adherence was evaluated by flow cytometry. In vivo, thrombocytopenia and lung seeding were assessed 30 min and 18 days, respectively, after i.v. injection of Lewis Lung carcinoma (LL2) cells into control or murine 7E3 F(ab')(2) (6 mg/ kg) athymic rats. Maximal in vitro platelet activation (72% serotonin release) occurred 30 min after adding platelets to tumor cells. At this time, 87% of the A375 cells had adhered to platelets. Abciximab significantly (P<0.05) reduced platelet adherence to tumor cells as evidenced by flow cytometry. Incubation of A375 cells with platelets induced VEGF release in a time-dependent manner. This release was significantly inhibited by Abciximab (81% at 30 min; P<0.05). In the presence of fibrinogen and FII, VEGF release induced by A375 (TF+) cells was significantly higher than that induced by KG1 (TF-) cells (105.5+/-24 vs. 42+/-7 pg/ml; P<0.001). Omitting fibrinogen or FII from the reaction mixture markedly decreased VEGF release. In vivo, GpIIb/IIIa blockade with murine 7E3 F(ab')(2) reduced LL2 tumor cell-induced thrombocytopenia by 90% (P<0.001) and lung seeding by 82% (P<0.05). We conclude that TF-bearing tumor cells can activate platelets largely via thrombin generation, and that such activation is associated with release of VEGF. This may enhance metastasis, possibly by increasing extravasation at points of adhesion to vascular endothelium.

Journal Article↗
PubMed1991

Omega-3 fatty acids: comparison of plant and seafood sources in human nutrition.

Omega-3 Fatty acids (omega-3FAs) are found in seafoods, some plants, and some livestock rations. Fish oils are the only concentrated source of eicosapentaenoic acid (EPA; 20:5 omega-3) and docosahexaenoic acid (DHA; 22:6 omega-3). The major omega-3FA in plants is alpha-linolenic acid (LNA; 18:3 omega-3). LNA must be converted to EPA before it exerts biological effects similar to EPA, such as reduced platelet aggregation. Human beings convert LNA to EPA to a small extent only. LNA may be more readily oxidized than incorporated into tissues. The effects of consuming LNA-rich oils are more modest than the effects of EPA-rich oils. Evidence suggests that omega-3FAs are essential and highly desirable for brain and eye development and heart health. LNA is the only source of omega-3FAs for vegetarians. Because LNA and EPA are not biologically equivalent, food composition data or product claims mentioning total omega-3FA content must clarify the individual omega-3FAs present.

Animals↗
PubMedDate not supplied

Pulmonary epithelial cell proliferation in primary culture of alveolar type II cells.

A small subpopulation of pulmonary epithelial cells (PE) proliferates in low-density primary culture of alveolar type II cells and forms colonies of cells that could be passaged for several generations and that in some respects maintain a differentiated phenotype of the alveolar type II cells. At this time it is not known if these cells are some form of progenitor epithelial cells or type II cells that are not fully differentiated in vitro. The proliferation of the PE cells was dependent on serum, alveolar macrophage-conditioned medium, and insulin being included in the culture medium. Under these conditions, approximately 0.5-1.0% of the seeded cells that adhered to the culture dishes were capable of forming colonies. Efficiency of colony formation increased to 5-10% in subsequent passages. PE cells maintained a high level (> 40%) of saturated phosphatidylcholine (PC) as a percentage of total PC throughout the culture period (> 28 days). However, the saturated PC content was not constant throughout the long-term culture period and the subsequent passages (41.3% at 29 days and 37.3% in the 3rd passage). These cells also contained numerous lamellar bodies and were able to bind the Maclura pomifera lectin. PE cells also expressed cytokeratin No. 19, as well as alkaline phosphatase activity, both possible markers for differentiated type II cells. However, PE cell synthesized low levels of Pg (approximately 2%), were squamous, and tended to form multiple strata, unlike the cuboidal type II cells in vivo. The cells did not exhibit immunocytochemically demonstrable surfactant-associated protein A (SP-A). Additional factors and culture requirements may be necessary for complete maturation of cultured PE cells. This was demonstrated by culturing PE cells on EHS matrix. Aggregates of cells surrounding a central lumen were formed after a few hours in culture and were maintained for 20 days. The cells contained lamellar bodies and some intercellular junctions. PE cells can be regarded as a highly selected subpopulation of pulmonary epithelial cells that concomitantly maintain proliferation and aspects of differentiated alveolar type II cells in long-term culture.

Animals↗
PubMed2003

Effects of root-end filling materials on fibroblasts and macrophages in vitro.

OBJECTIVE: The aim of this study was to investigate the effects of 4 root-end filling materials (mineral trioxide aggregate [MTA], intermediate restorative material [IRM], amalgam, and Retroplast) on cell growth, cell morphology, and cytokine (interleukin [IL]1beta and IL-6) production in mouse fibroblasts and macrophages. STUDY DESIGN: Millipore culture plate inserts with freshly mixed or set root-end filling material were placed into 6-well cell culture plates with already attached mouse fibroblasts or macrophages. Cells cultured with only the Millipore culture plate inserts served as a control. After a 3-day incubation, cell morphology was examined, and the total cell number per well was counted and analyzed by using 1-way analysis of variance. For cytokine assay, mouse macrophages were incubated in 24-well flat-bottom plates with set root-end filling material disks in the bottom. Cells cultured without the material disks served as negative controls, and cells cultured with lipopolysaccharides served as positive controls. After 24-hour incubation, culture media were collected for cytokine assay by using enzyme-linked immunosorbent assay. RESULTS: All root-end filling materials inhibited the cell growth of mouse fibroblasts and macrophages. There was no growth in the originally seeded cells in the fresh IRM, the fresh Retroplast, and the set IRM group. There was no difference between MTA and amalgam for cell growth either in the fresh material groups or in the set material groups. The total cell number in the set Retroplast group was significantly less than that in the set MTA group. Morphologically, MTA was characterized by denatured medium proteins and dead cells adjacent to the material, which were observed only in the fresh MTA group. There was no detected cytokine production in any of the tested material groups. CONCLUSION: All root-end filling materials inhibited cell growth, and none induced IL-1beta and IL-6 production.

Aluminum Compounds↗
PubMed1986

Cell-substratum and cell-cell interactions promote testicular peritubular myoid cell histotypic expression in vitro.

Peritubular cells, prepared from seminiferous tubules from testes of 20-day-old-rats, were seeded onto different substrata and cultured under varying conditions. When plated onto polystyrene or glass surfaces, peritubular cells assumed a typical fibroblast-like cell shape and cell association pattern, together with a fibroblast-like migration behavior. They maintained high rates of proliferation even after achieving confluency. In contrast, when peritubular cells were plated onto a seminiferous tubule biomatrix (ST-biomatrix) surface, they spread to form a continuous cell layer having a myoepithelioid histotype similar to that of peritubular myoid cells in the intact seminiferous tubule. The characteristics of the myoepithelioid histotype described include a squamous, polyhedral cell shape; a cobblestone-like cell association pattern, with closely apposing or slightly overlapping cell borders, and a very low mitotic index. When peritubular cells were plated onto laminin, collagen, fibronectin, heparin, or a liver biomatrix, a fibroblast-like pattern resulted, indicating that ECM components listed and liver biomatrix are unable to substitute for ST-biomatrix in maintaining normal myoepithelioid characteristics in vitro. In cocultures of Sertoli cells plated on top of peritubular cells, the peritubular cells directly in contact with Sertoli cell aggregates developed a myoepithelioid histotype, whereas peritubular cells in regions not in direct contact had a fibroblast-like histotype. The data are discussed in relation to the possible role of cell-cell interactions, and cell-substratum interactions, in the acquisition and stabilization of the histotype of peritubular cells in the seminiferous tubule during development.

Animals↗
PubMed2005

Lithopanspermia in star-forming clusters.

This paper considers the lithopanspermia hypothesis in star-forming groups and clusters, where the chances of biological material spreading from one solar system to another is greatly enhanced (relative to action in the field) because of the close proximity of the systems and lower relative velocities. These effects more than compensate for the reduced time spent in such crowded environments. This paper uses approximately 300,000 Monte Carlo scattering calculations to determine the cross sections for rocks to be captured by binaries and provides fitting formulae for other applications. We assess the odds of transfer as a function of the ejection speed v (eject) and number N(.) of members in the birth aggregate. The odds of any given ejected meteoroid being recaptured by another solar system are relatively low, about 1:10(3)-10(6) over the expected range of ejection speeds and cluster sizes. Because the number of ejected rocks (with mass m > 10 kg) per system can be large, N (R) approximately 10(16), virtually all solar systems are likely to share rocky ejecta with all of the other solar systems in their birth cluster. The number of ejected rocks that carry living microorganisms is much smaller and less certain, but we estimate that N (B) approximately 10(7) rocks can be ejected from a biologically active solar system. For typical birth environments, the capture of life-bearing rocks is expected to occur N (bio) asymptotically equal to 10-16,000 times (per cluster), depending on the ejection speeds. Only a small fraction (f (imp) approximately 10(4)) of the captured rocks impact the surfaces of terrestrial planets, so that N (lps) asymptotically equal to 10(3)-1.6 lithopanspermia events are expected per cluster (under favorable conditions). Finally, we discuss the question of internal versus external seeding of clusters and the possibility of Earth seeding young clusters over its biologically active lifetime.

Astronomical Phenomena↗
PubMed1982

Factors that influence initiation and growth of 9L rat brain gliosarcoma multicellular spheroids.

This report details optimum conditions for initiating and growing 9L rat brain gliosarcoma multicellular spheroids. Best results were achieved when 0.5 to 2.0 x 10(6) cells were seeded initially into agarose (0.5 to 1.0%)-coated Petri dishes. Spheroids initiated in this manner appeared to grow in spinner culture at a rate slightly faster than spheroids initiated and grown in spinner culture. An optimum growth rate was obtained for individual spheroids grown in the well of cluster dishes coated with 0.5 to 0.75% agarose in growth medium containing 10% newborn calf serum and 0.9 g glucose per liter. Three methods for dissociation of spheroids at both room temperature and 37 degrees have been developed. The "race track" method of fractional dissociation produced a constant and similar number of cells for each disaggregation interval, and the plating efficiency of cells in each fraction was similar.

Animals↗