Search results for "Acellular"
showing 10 items of 1986 documents
Growth-related changes of oxygen consumption rates of tumor cells grown in vitro and in vivo
1989
Growth-related changes of oxygen consumption rates of tumor cells, grown in vitro or in vivo, were investigated. For in vitro investigations, L929 and DS-carcinosarcoma cells were cultured in artificial media. For in vivo studies, DS-carcinosarcoma cells were implanted into the abdominal cavity of Sprague-Dawley rats (ascites tumor, containing malignant cells, leukocytes, lymphocytes, and macrophages). Oxygen uptake was measured photometrically. Parameters of the extracellular medium judged to possibly influence the respiratory activity of tumor cells were monitored at different growth stages (glucose, lactate, and amino acid levels, oxygen and carbon dioxide partial pressures, and pH value…
Membrane potential of rat calvaria bone cells: dependence on temperature.
1990
The membrane potentials of bone cells derived from calvaria of new born rats was shown to be strongly dependent on temperature. When we lowered the temperature from 36 degrees C to 26 degrees C, cells with spontaneous resting membrane potentials (MP) of -80 to -50 mV depolarized (mean amplitude 8 mV; n = 33), and the membrane resistance increased by approximately 80% (n = 20). The temperature response depended on the actual MP, the reversal potential being in the range of -80 to -90 mV. With the application of ouabain (0.1-1 mmol/liter; n = 12), cells depolarized. Simultaneously, the reversal potential of the temperature response was shifted towards more positive values and approached the a…
Na+ -dependent neutral amino acid transporters A, ASC, and N of the blood-brain barrier: mechanisms for neutral amino acid removal.
2004
Four Na+-dependent transporters of neutral amino acids (NAA) are known to exist in the abluminal membranes (brain side) of the blood-brain barrier (BBB). This article describes the kinetic characteristics of systems A, ASC, and N that, together with the recently described Na+-dependent system for large NAA (Na+-LNAA), provide a basis for understanding the functional organization of the BBB. The data demonstrate that system A is voltage dependent (3 positive charges accompany each molecule of substrate). Systems ASC and N are not voltage dependent. Each NAA is a putative substrate for at least one system, and several NAA are transported by as many as three. System A transports Pro, Ala, His,…
Review: How was metazoan threshold crossed? The hypothetical Urmetazoa.
2001
The origin of Metazoa remained — until recently — the most enigmatic of all phylogenetic problems. Sponges [Porifera] as ‘living fossils’, positioned at the base of multicellular animals, have been used to answer basic questions in metazoan evolution by molecular biological techniques. During the last few years, cDNAs/genes coding for informative proteins have been isolated and characterized from sponges, especially from the marine demosponges Suberites domuncula and Geodia cydonium. The analyses of their deduced amino acid sequences allowed a molecular biological resolution of the monophyly of Metazoa. Molecules of the extracellular matrix/basal lamina, with the integrin receptor, fibronec…
Identification of the Weevil immune genes and their expression in the bacteriome tissue
2008
Abstract Background Persistent infections with mutualistic intracellular bacteria (endosymbionts) are well represented in insects and are considered to be a driving force in evolution. However, while pathogenic relationships have been well studied over the last decades very little is known about the recognition of the endosymbionts by the host immune system and the mechanism that limits their infection to the bacteria-bearing host tissue (the bacteriome). Results To study bacteriome immune specificity, we first identified immune-relevant genes of the weevil Sitophilus zeamais by using suppressive subtractive hybridization (SSH) and then analyzed their full-length coding sequences obtained b…
Extracellular membrane vesicles as a mechanism of cell-to-cell communication: advantages and disadvantages.
2014
Microvesicles represent a newly identified mechanism of intercellular communication. Two different types of microvesicles have been identified: membrane-derived vesicles (EVs) and exosomes. EVs originate by direct budding from the plasma membrane, while exosomes arise from ectocytosis of multivesicular bodies. Recent attention has focused on the capacity of EVs to alter the phenotype of neighboring cells to make them resemble EV-producing cells. Stem cells are an abundant source of EVs, and the interaction between stem cells and the microenvironment (i.e., stem cell niche) plays a critical role in determining stem cell phenotype. The stem cell niche hypothesis predicts that stem cell number…
The fungal elicitor cryptogein is a sterol carrier protein
1997
AbstractCryptogein is a protein secreted by the phytopathogenic pseudo-fungus, Phytophthora cryptogea. It is a basic 10 kDa hydrophilic protein having a hydrophobic pocket and three disulfide bridges. These common features with sterol carrier proteins led us to investigate its possible sterol transfer activity using the fluorescent sterol, dehydroergosterol. The results show that cryptogein has one binding site with strong affinity for dehydroergosterol. Moreover, this protein catalyzes the transfer of sterols between phospholipidic artificial membranes. This is the first evidence for the existence of an extracellular sterol carrier protein and for a molecular activity of cryptogein. This p…
Modulation of the Biological Activity of a Tobacco LTP1 by Lipid Complexation
2004
Plant lipid transfer proteins (LTPs) are small, cysteine-rich proteins secreted into the extracellular space. They belong to the pathogenesis-related proteins (PR-14) family and are believed to be involved in several physiological processes including plant disease resistance, although their precise biological function is still unknown. Here, we show that a recombinant tobacco LTP1 is able to load fatty acids and jasmonic acid. This LTP1 binds to specific plasma membrane sites, previously characterized as elicitin receptors, and is shown to be involved in the activation of plant defense. The biological properties of this LTP1 were compared with those of LTP1-linolenic and LTP1-jasmonic acid…
Characterization of the metastatic properties of two methylcholantrene-induced fibrosarcoma in mice
1988
MC1 and MC2 murine fibrosarcomas, following intramuscular innplantation in mice, release different numbers of tumor cells into the bloodstream and differ in their lung colonization potential following intravenous inoculation. Since these biological properties could be related to a different degree of maligancy, in vivo and in vitro experiments were performed vvith these two tunnors in an attempt to correlate their spontaneous metas-tatic potential with other parameters related to tunnor cell invasion and metastasis. Following intramuscular inplantation the MC2 fibrosarcoma was observed to have a slow but progressive ability to spontaneously metastasize while the MC1 lacked this capability. …
A new automated plunger for cryopreparation of proteins in defined - even oxygen free - atmospheres
2009
We study the structure and function of hemocyanins. They are giant extracellular oxygen carriers in the hemolymph of many molluscs and arthropods. Since some of these blue, copper-containing proteins show the highest cooperativity in nature (h = 10), one of our goals is to understand the chemomechanical interaction between the different substructures during allosteric oxygen binding.