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At least 235 records · Page 13Linked to original sources
PubMed1993

Role and innocuity of Tisseel, a tissue glue, in the grafting process and in vivo evolution of human cultured epidermis.

Cultured epidermal sheets are currently used for burn wound treatment but reported results on graft take are variable. This study was designed to evaluate the role and influence of Tisseel, a fibrin glue, in the take of cultured human epidermal sheets in an athymic mouse model. On days 4, 10 and 21 post-grafting, histology, electron microscopy and immunofluorescence staining confirmed the presence of a human epithelium and the development of a basement membrane. Tisseel was detectable on day 4 only, but overall treated and untreated grafts were similar. The use of Tisseel enhanced the mechanical stability of these fragile grafts, increased the percentage of graft take, and its innocuity on the in vivo evolution of cultured epidermal sheets was demonstrated. For these reasons, we think that Tisseel may be advantageous in a clinical setting.

Animals↗
PubMed2006

Ripples in a pond: an open system model of the evolution of safety culture.

The development of an effective safety culture is essential to promote safe operations. Previous studies have either identified the characteristics of effective safety culture analytically, inferring them from signs and symbols derived from working practices, or have restricted the study of the development of safety culture to workers within an organisation. This paper describes a large-scale survey-based study in which the factors influencing the evolution of safety culture are identified empirically and, drawing upon open systems theory, are also extended beyond the bounds of the organisation. Three major determinants of safety culture are identified: safety concerns, influences and actions. Sub-components within each of these categories are also identified and the relationship between them is hypothesised.

Adult↗
PubMed1989

Hydrogen evolution of Enterobacter aerogenes depending on culture pH: mechanism of hydrogen evolution from NADH by means of membrane-bound hydrogenase.

The pH dependency of cell mass productivity, the hydrogen evolution rate and the yield of hydrogen from glucose was measured by controlling the pH of the culture automatically. The cell mass productivity of Enterobacter aerogenes increased in a linear fashion up to a pH value of approx. 7.0. In contrast, both the evolution rate and the yield of hydrogen showed convex relationships up to a pH value of 7.0, both having maximum values at a pH of approx. 5.8. The maximum evolution rate was approx. 11.3 mmol H2 per g dry cell per h at 38 degrees C. A hypothetical mechanism for hydrogen evolution was proposed by taking our results and other research work into consideration. The proposed mechanism of hydrogen evolution was that NADH was oxidized on the inside surface of the cell membrane and protons were reduced on the outside surface by means of membrane-bound hydrogenase. This mechanism explains in a thermodynamic context the relation between the activity of the hydrogen evolution and the pH of the culture.

Cell Membrane↗
PubMed1980

General theory of evolution.

The biological, neural, cultural and technical evolutions and their phenomena have been explored, and on the basis of our findings the formation of a general theory of evolution has been undertaken. In each of the systems studied, the presence of structural building units, excitable structures and an energy-flow going through the system can be observed. Under the organizing effect of this energy-flow, the spontaneous generation of the replicative information begins and the structures of the system establish functional relations with each other. It can be demonstrated that the evolution of structures has a replicative character. The evolution goes through a phase of non-identical replication, and reaches the phase of identical replication. The parts of the system become separated, that is, compartments develop within it. The replicative information becomes compartmentalized and it converges. As a consequence of the convergence, the compartments compose new structural units which is tantamount to the development of new evolutional levels. The direction of evolution is determined by the growth of replicative information, and this process is concluded when the total system becomes one replicative unit. In the last part of the paper a few of the basic principles of evolution concerning matter, energy and information are drawn up.

Animals↗
PubMed2006

Optimising the therapeutic safety of human embryonic stem cells through the evolution of defined culture systems supporting their isolation.

Realising the therapeutic promise of embryo-derived stem cells is absolutely dependent on the evolution of defined and quality assured in vitro culture systems to mediate their isolation, expansion and delivery. Critical to the safety of these systems, both for the transplant recipient and the general population, is the necessity to eliminate dependence on animal cell-derived reagents to reduce the risk of cross-specific disease transmission. This paper discusses progress in the development of defined culture systems for human embryonic stem cell isolation and the challenges that still must be overcome.

Animals↗
PubMed1994

Cycles, chaos, and evolution in virus cultures: a model of defective interfering particles.

Defective interfering particles (DIP) are spontaneous deletion mutants of viruses that replicate at the expense of the parent virus. DIP have complex effects on the growth of viruses in vitro, including the establishment of persistent infection, cyclical variation in virus titer, eradication of replicating virus, and rapid evolution of the virus. We show here that a simple mathematical model, based only on experimental observations, can explain all of the major effects of DIP on the population dynamics of virus growth. The variation in virus titer caused by DIP has many features that are characteristic of deterministic chaos: it follows that the quantitative effects of DIP are intrinsically unpredictable beyond a short time. We conclude (i) that other factors, such as temperature-sensitive virus mutants or interferons, need not be invoked to explain the complex effects of DIP; and (ii) that dominantly interfering viruses should only be used with great caution for therapeutic purposes, since their effects are, in principle, unpredictable.

Biological Evolution↗
PubMed2004

Characterization of multiple members of the HSP70 family in platyfish culture cells: molecular evolution of stress protein HSP70 in vertebrates.

A shift from 28 to 37 degrees C in the incubation temperature of a culture of the platyfish fibroblast cell line, EHS cells (platyfish fibroblast cell line), induced a set of stress proteins. A two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) analysis showed that the cells expressed three genetically distinct forms of heat-shock protein 70 (HSP70) family proteins: heat-inducible forms of HSP70, the constitutively expressed heat-shock cognate protein 70 (HSC70) and its phosphorylated isoform, and the glucose-regulated protein 78 (GRP78). Three different clones encoding two major isoforms of heat-inducible HSP70, platyfish HSP70-1 and HSP70-2, and of the HSC70 were isolated from a platyfish cDNA library. We compared the deduced amino acid sequences of the platyfish HSP70 and HSC70 proteins with those of other vertebrates. Phylogenetic analysis showed that vertebrate HSP70 could be classified into four cluster groups: (a) fish HSP70, with two isoforms of heat-inducible HSP70 in fish, fish HSP70-1 and HSP70-2; (b) the mammalian testis-specific HSP70-related protein HST70; (c) the mammalian heat-inducible HSP70B'; and (d) the mammalian major histocompatibility complex (MHC)-linked HSP70, including the MHC-linked heat-inducible HSP70 and the testis-specific HSP70-related protein. These findings suggest that vertebrate HSP70 was derived from a single ancestral HSP70 gene during vertebrate evolution and that multiple copies of heat-inducible HSP70 were probably evolved during genetic divergence in fish and higher vertebrates.

Amino Acid Sequence↗
PubMed1985

Autocatalysis in cultural ecology: model ecosystems and the dynamics of biocultural evolution.

Using a well-known mathematical model frequently applied in theoretical population dynamics, certain ecological mechanisms are investigated that are inherent in the organic evolution of cultural capacities in man. Culture is argued to involve ecological interactions exhibiting analogies to the interaction of chemical species in autocatalytic biomolecular reactions. In the model, biocultural evolution proceeds by more and more broadening ecological niches and, thus, releasing competitive selection pressure on the populations involved. This, in turn, facilitates the maintenance of polymorphism in these populations as well as the individual acquisition of organic traits through learning and cultural transmission. The result is that the genetic variance in phenotypic expressions decreases at an accelerated rate.

Cultural Evolution↗
PubMed1992

Use of fluorescence anisotropy determinations for indicating the physiological status of hybridoma cell cultures.

The evolution of lipid compartment fluidity during culture of hybridoma cells was studied by fluorescence polarization measurements. The probe partition between the plasma membrane and intracytoplasmic compartments was determined by a quenching fluorescence method. A progressive decrease of the plasma membrane fluidity was observed during the growth phase with an increase during stationary and degeneration phases of the culture. These data suggest that fluidity parameters could be used to follow the behaviour of hybridoma cell cultures.

Cell Membrane↗
PubMed2005

Use of enrichment culture for directed evolution of the Vibrio fluvialis JS17 omega-transaminase, which is resistant to product inhibition by aliphatic ketones.

A novel high-throughput screening method that overcame product inhibition was used to isolate a mutant omega-transaminase from Vibrio fluvialis JS17. An enzyme library was generated using error-prone PCR mutagenesis and then enriched on minimal medium containing 2-aminoheptane as the sole nitrogen source and 2-butanone as an inhibitory ketone. An identified mutant enzyme, omega-TAmla, showed significantly reduced product inhibition by aliphatic ketone. The product inhibition constants of the mutant with 2-butanone and 2-heptanone were 6- and 4.5-fold higher than those of the wild type, respectively. Using omega-TAmla (50 U/ml) overexpressed in Escherichia coli BL21, 150 mM 2-aminoheptane was successfully resolved to (R)-2-aminoheptane (enantiomeric excess, >99%) with 53% conversion with an enantioselectivity of >100.

Amines↗
PubMed2003

Hydrocarbons and the evolution of human culture.

Most of the progress in human culture has required the exploitation of energy resources. About 100 years ago, the major source of energy shifted from recent solar to fossil hydrocarbons, including liquid and gaseous petroleum. Technology has generally led to a greater use of hydrocarbon fuels for most human activities, making civilization vulnerable to decreases in supply. At this time our knowledge is not sufficient for us to choose between the different estimates of, for example, resources of conventional oil.

Animals↗
PubMed1999

The conditions for tool use in primates: implications for the evolution of material culture.

In order to identify the conditions that favored the flourishing of primate tool use into hominid technology, we examine inter- and intraspecific variation in manufacture and use of tools in extant nonhuman primates, and develop a model to account for their distribution. We focus on tools used in acquiring food, usually by extraction. Any model for the evolution of the use of feeding tools must explain why tool use is found in only a small subset of primate species, why many of these species use tools much more readily in captivity, why routine reliance on feeding tools is found in only two species of ape, and why there is strong geographic variation within these two species. Because ecological factors alone cannot explain the distribution of tool use in the wild, we develop a model that focuses on social and cognitive factors affecting the invention and transmission of tool-using skills. The model posits that tool use in the wild depends on suitable ecological niches (especially extractive foraging) and the manipulative skills that go with them, a measure of intelligence that enables rapid acquisition of complex skills (through both invention and, more importantly, observational learning), and social tolerance in a gregarious setting (which facilitates both invention and transmission). The manipulative skills component explains the distribution across species of the use of feeding tools, intelligence explains why in the wild only apes are known to make and use feeding tools routinely, and social tolerance explains variation across populations of chimpanzees and orangutans. We conclude that strong mutual tolerance was a key factor in the explosive increase in technology among hominids, probably intricately tied to a lifestyle involving food sharing and tool-based processing or the acquisition of large, shareable food packages.

Animals↗