Formation Of New Cells Research Articles

Epigenetic change: new from the seeds of the old

Abstract This paper argues against the division of the perception of change into two dominant forms in the strategic change literature, incremental and paradigmatic. It argues that rather than the either/or nature of the incremental and paradigmatic change interpretation, there is a continuum of levels of real world change, with every change being capable of being interpreted as incremental at one aspirational level and paradigmatic at another. The paper argues for a new type of change, termed ‘epigenetic change’. Epigenesis is the organic formation of new cells from existing cells. Epigenetic change is therefore partly within and partly outside recipe change. Epigenesis implies discontinuity, but where the old contains the seed of the new. It is argued that change can take place at three levels: incremental change, epigenetic change and paradigmatic change. Copyright © 2003 John Wiley & Sons, Ltd.

Adult Stem Cell Plasticity Defined

After completing this article, readers should be able to: 1. Define stem cell characteristics and the three separate classes of stem cells. 2. Define stem cell plasticity. 3. Describe four possible mechanisms of stem cell plasticity. 4. Describe clinical situations that may benefit from stem cell therapy. 5. Delineate areas of research that are needed to make feasible the use of adult stem cells for clinical therapy Investigators have postulated since the turn of the century that some cells in the body appear to participate in the formation of new cells to replace injured, aged, or infected cells in tissues and organs. The concept that certain specialized cells within an organ (stem cells) could give rise to mature functioning cells in that same organ has been demonstrated most clearly in the hematopoietic system. Evidence for stem cell function in the hematopoietic system has come from controlled laboratory experiments and as a consequence of human exposure to massive irradiation during armed conflict. World War II was brought to an end dramatically in August 1945 with the dropping of atomic bombs on the cities of Hiroshima and Nagasaki, Japan. In the wake of the devastation and human suffering of these events, several hundred thousand Japanese civilians and soldiers were exposed to lethal and sublethal doses of irradiation. Examination of the affected people included, but was not limited to, the ablative effects of irradiation on the body’s hematopoietic system. Observation and treatment of these patients led to several scientific reports confirming the postulated existence of stem cells that are responsible for the continuous production of all circulating blood cells. Subsequent studies performed on laboratory rodents detailed the detrimental effects of irradiation on the hematopoietic system as well as the ability of bone marrow transplantation to correct such anomalies. Hematopoietic repopulation was established by transplanting clonogenic marrow cells, which …

Growth of cell populations of the intralobular duct in the submandibular gland of the mouse during postnatal development.

The growth of cell populations of intercalated ducts (ID), striated ducts (SD) and convoluted granular tubules (CGT) of the submandibular gland of the mouse was analyzed, during the period of 14 to 84 days of postnatal life, by means of morphometric methods. The absolute number of cells in each type of duct was submitted to curve fitting by means of linear regression analysis, and the obtained equations were: y = 13.22 + 0.87x for ID cells in the growth period of 14 to 84 days; y = -18.82 + 3.69x and y = 176.03 - 1.93x for SD cells in the periods of growth and decay of cells, from 14 to 35 and 35 to 84 days, respectively; and y = 90.59 + 4.60x for CGT cells in the growth period of 28 to 84 days. Based on these equations, the daily accumulation (growth rate) or loss (decaying rate) of cells in the period covered by each equation was calculated. Thus, the rate of growth of ID cells was 0.87 x 10(5) cells/day; the growth and decline rates of SD cells were 3.69 x 10(5) cells/day and -1.93 x 10(5) cells/day, respectively; and the growth rate of CGT cells was 4.60 x 10(5) cells/day. The analysis of the accumulation or loss of cells and the balance of cell populations in the various types of ducts revealed that SD cells were transformed into CGT cells and that the growth of these cells population also depends on the formation of new cells through proliferative activity, probably in the intercalated ducts.

Characteristics of shear bands formed in an austenitic stainless steel during hot deformation

A detailed investigation of the substructural characteristics of shear bands, formed in an austenitic stainless steel during deformation in torsion at 900°C, with particular emphasis on their nucleation stages, has been undertaken. Shear bands forming at large strains in a matrix of pre-existing microbands are composed of well-recovered, slightly elongated cells. These bands propagate along a similar macroscopic path and the cells, present within their substructure, are rotated relative to the surrounding matrix about axes close to a common macroscopic direction. The cell boundaries are frequently non-crystallographic, suggesting that the cells might often form through the operation of multiple slip. Shear bands appear to form through a cooperative nucleation of originally isolated cells that gradually interconnect with each other to form long, thin bands that subsequently thicken via the formation of new cells. When crossing a shear band, cumulative misorientations across consecutive cell boundaries display a typical sigmoidal profile, characterised by a gradual increase of misorientation angles to a peak value followed by a subsequent gradual decrease towards the matrix orientation. The formation of new cells thus appears to be assisted by the stress fields generated by lattice rotations of the previously formed cells.

Formation and Maintenance Processes of a Stationary Band-shaped Heavy Rainfall Observed in Niigata on 4 August 1998.

On 4 August 1998, a torrential rainfall was observed in the Niigata area, in central Japan. The rainfall was induced by a quasi-stationary rainband aligned in the east-southeast direction from the west of Sado Island. The rainband lasted for several hours with the characteristic features of a back-building formation, in which new convective cells were successively generated in an upstream direction. The rainfall area and intensity simulated by a nonhydrostatic mesoscale model with a 5-km horizontal grid agreed well with the observation. The rainband with a back-building nature was reproduced successfully by a nonhydrostatic model with a 2-km grid. The simulation results showed that the heavy rainfall formed as a result of strong convective instability enhanced by low-level humid and middle-level dry inflows from the southwest into the weak convergence region associated with the Baiu frontal zone. Sensitivity experiments indicated that neither the terrain of Sado Island, nor the evaporative cooling of raindrops affected the formation of the rainband. Although moved to the downstream when the low-level wind convergence was not enhanced enough, the simulated rainband stagnated after the convergence became so strong that the whole low-level air could be lifted upward while crossing the convergence zone. Therefore, the quasi-stationary rainband was maintained by the convection-enhanced low-level wind convergence existing upstream of the rainband. Over the convergence zone associated with the quasi-stationary rainband, new convective cells successively formed and separated from the zone after having developed higher. This successive formation of new cells could maintain a back-building formation. Such a back-building formation was found at several points over the wind convergence zone. These meso-β-scale convective systems with a back-building nature produced the precipitation region with a length over 200 km.

A radar data based short-term rainfall prediction model for urban areas — a simulation using meso-scale meteorological modelling

A conceptual short-term rainfall prediction model for urban catchments is presented. The only input variables are surface rainfall and vertically integrated liquid water content (VIL), both measurable by radar on site. The forecast is based on simple mass balancing of water within air columns and the spatial advection of the variables using information from consecutive time steps. This paper describes a qualitative study, in which the conceptual model is tested within an idealised numerical framework: instead of using observed and potentially noisy radar data, it is initialised with output from a three-dimensional physically based meso-scale meteorological model. The meteorological model provides the microphysical data as well as detailed information on the dynamics and structure of the atmosphere, which are generally not available with observational data. The performance of the prediction model is assessed with regard to different types of rainfalls as well as respond time of the catchments. First results suggest that the conceptual model is capable of qualitatively predicting future surface rainfall development, including formation of new cells, cell splitting and decay. There is also indication that the conceptual model performs better than simple advection routines for lead times that correspond roughly to the respond times of the catchments. The results lead to the conclusion that the information of VIL may be useful for quantitative rainfall prediction, and that the conceptual model should be further developed and tested with real radar data.

Physiology of Saccharomyces cerevisiae during cell cycle oscillations

Synchronized populations of Saccharomyces cerevisiae CBS 426 are characterized by autonomous oscillations of process variables. CO 2 evolution rate, O 2 uptake rate and heat production rate varied by a factor of 2 for a continuous culture grown at a dilution rate of 0.10 h −1. Elemental analysis showed that the carbon mass fraction of biomass did not change. Since the reactor is not at steady state, the elemental and energy balances were calculated on cumulated quantities i.e. the integral of the reaction rates. It was possible to show that carbon, degree of reduction and energy balances matched. Application of simple mass balance principles for non-steady state systems indicated that oscillations were basically characterized by changes in biomass production rate. In addition, the amount of intermediates e.g. ethanol or acetate, produced or consumed was negligible. Growth rate was low during the S-phase (0.075 h −1) and high during the G2, M and G1 phases (0.125 h −1) for a constant dilution rate of 0.10 h −1. However, nitrogen, ash, sulfur and potassium content showed systematic increases during the S-phase (bud initiation). Cell component analyses showed that changes in cellular fractions during oscillations (storage carbohydrate content decreased during the S-phase) were due to changes in production rates, particularly for protein and carbohydrates. Nevertheless, using the data evaluation techniques for dynamic systems presented here, it was shown that storage carbohydrates are not consumed during the S-phase. Only the synthesis rate of the different cell components changed depending on position in cell cycle. The growth process may be divided into two phenomena: the formation of new cells during mitosis with a low yield, and size increase of new born cells with high yield. Both kinetic and stoichiometric coefficients varied with the position in the oscillation: the results showed that biomass structure changed and that specific growth rate, as well as biomass yield, varied by ± 25% during the oscillation.

Regeneration of rat corneal epithelium is delayed by the inhibitory epidermal pentapeptide (EPP)

The effect of the inhibitory epidermal pentapeptide (EPP) on regeneration of rat corneal epithelium was studied over a 24-h period after removal of the central part of the corneal epithelium by means of n-heptanol and scraping. Both unphosphorylated and phosphorylated EPP inhibited the mitotic rate and the formation of new cells to the same extent. Thus, the mitosis inhibitor that originally was isolated from mouse epidermis, acts even on the ectodermally derived corneal epithelial cells.

Kinetics of gastric epithelial cells in duodenal ulcer: local environmental factors controlling the proliferation and differentiation of gastric epithelial cells.

The Pathophysiology of peptic ulcer disease is based on heterogenous abnormalities of gastric epithelial cell function. Based on clinical observations, we proposed the hypothesis that duodenal ulcer can occur with normal acid secretion, but that recurrence of duodenal ulcer may be caused by genetic and environmental factors that promote altered kinetics in gastric cells; i.e., the formation of new cells, the migration of cells, and changes in their life span of cells. The factors controlling these processes include feeding, the action of endocrine and gut hormones, the action of the autonomic nervous system, the microcirculation, and growth factors. In this review, to prove our hypothesis, we have summarized the clinical and experimental approaches to reveal the environmental factors that control the proliferation and differentiation of gastric epithelial cells.

Decreased cell replication and polyamine content in insulin-producing cells after exposure to human interleukin 1 beta.

Interleukin 1 (IL-1) has been suggested to cause the islet B cell destruction occurring during the development of insulin-dependent diabetes mellitus. One mechanism by which B cell loss can be compensated for is via de novo formation of new cells through replication. In the present study the replicatory activity of cells in isolated rat pancreatic islets and in the insulin-producing cell line RINm5F has been assessed by [3H]thymidine incorporation methods after exposure to 1-25 U/ml of human recombinant IL-1 beta (rIL-1 beta). In the rat islets [3H]thymidine incorporation was decreased by 20% 5 h after exposure to 25 U/ml rIL-1 beta. A similar inhibition was also observed in islets exposed to 2.5 and 12.5 U/ml rIL-1 beta. In the RINm5F cells there was a dose-dependent inhibition of the cell replication to approximately 50% of the controls in cells exposed to 25 U/ml rIL-1 beta for 48 h. This was also accompanied by an increased cell death, as measured by trypan blue inclusion (controls 13% and rIL-1 beta treated cells 25%). The insulin content of the RINm5F cells was reduced by about 40% after a 48-h exposure to 25 U/ml rIL-1 beta. When the exposure of the RINm5F cells to rIL-1 beta was decreased to 24 h there was no increased cell death, but a reduced replicatory activity was still observed. rIL-1 beta decreased the cellular content of the polyamines spermidine and spermine.(ABSTRACT TRUNCATED AT 250 WORDS)

Spatial distribution of glutamate, taurine and GABA in teleosts and mammals retina: In vivo and in vitro study

Teleost and amphibian retina grows throughout life at the circumferential margin distal to the center. Retinas of two teleosts, goldfish and Eugerres plumieri; and two mammals, rat and rabbit were dissected into concentric regions; center and periphery, or center, intermediate and periphery. The concentration of glutamic acid, taurine, and gamma-aminobutyric acid was determined in these areas. A non-significant difference was found between the center and periphery of retinas dissected into two regions. By dissecting the teleost retina in three concentric regions a progressive increase of gammaaminobutyric acid and taurine for center to periphery was observed, which was statistically significant for taurine. Rat and rabbit retina did not present this difference. The concentration of these amino acids was also determined in two concentric regions of goldfish retina 24 hr after crush of the optic nerve. Taurine content significantly increased in the center of the regenerating retina, but not in the periphery. Outgrowth was measured in expiants prepared from central and peripheral retina in the presence of exogenous taurine. The amino acid produced an increase of the nerve growth index of central expiants, but inhibited the growth from peripheral expiants. This report presents a correlation between taurine concentration in a region of the retina that could be considered as embryonic tissue, suggesting that this amino acid plays a role in the formation of new cells. Moreover, the results from post-crush and cultured retina, with respect to taurine concentration or regenerating effect, suggest a saturation of the taurineenriched zone.

Increased DNA synthesis in adipocytes and capillary endothelium in rat adipose tissue during overfeeding.

Adult male rats were subjected to overfeeding with a high-fat, high-sugar diet for 3 and 7 days resulting in a moderate expansion of adipose tissue depots by an increase in fat-cell size. Seventeen hours and 7 days after injection of a pulse of labelled thymidine, specific activity of DNA was examined in different cellular fractions obtained from the epididymal and perirenal adipose tissues after collagenase liberation and separation procedures. A slow increase of formation of new adipocytes occurred after 3 and 7 days of overfeeding, most pronounced in cells from perirenal adipose tissue. Capillary endothelium and cells in the stromal fraction showed a rapid synthesis and turn-over. Overfeeding induced an increased formation of new capillary endothelial cells after 7 days of overfeeding, again most pronounced in perirenal cells. It was concluded that new fat cells are formed at a slow rate early during overfeeding. Capillary endothelium in adipose tissue has a high rate of turnover, and its synthesis is increased further by overfeeding. New adipocytes precede, and possibly stimulate, the formation of new capillaries. Formation of new cells in the remaining stromal-vascular cells is probably occurring at different rates among different types of cells.

Increased visualization of antral gastrin-producing G-cells after acute stimulation of gastrin release in the rat.

The effect of acute stimulation of gastrin release on the number of antral gastrin-producing G-cells stained by conventional immunohistology was investigated in two experimental models. The substituted benzimidazole derivate BY 308 was administered at a dosage that induces complete achlorhydria and thereby led to marked hypergastrinaemia. Two hours after drug administration, antral G-cell density was increased by 14% and 35% in 12-h and 48-h fasted rats, respectively. Both serum gastrin levels and G-cell density further increased after 3 and 8 days' treatment with BY 308 whereas the somatostatin (D)-cell count did not change prior to 8 days' administration. In the isolated, vascularly perfused rat stomach, acetylcholine was perfused for 36 min; this regimen increased gastrin release four-fold and enhanced the G-cell count by 24% whereas 8 min acetylcholine perfusion did not alter G-cell density significantly but stimulated gastrin output. The results of this study suggest that acute changes in the secretory activity of the gastrin cell are accompanied by an alteration of the staining characteristics thus indicating that an increase in the antral G-cell count does not solely depend upon formation of new cells.

The Benefit of Sleep

Our tissues are continuously decaying, and continuously being renewed. Decay and renewal are not equal at all times, but are subject to biological rhythms (circadian variation). Decay, degradation, breakdown or catabolism is maximal during wakefulness, while renewal or anabolism is maximal during sleep. Renewal depends upon protein synthesis, either for the formation of new cells in, for example, the skin; or for replacing the constituents of existing cells in, for example, the brain.

The non-eicosanoid functions of the essential fatty acids

Coincident with the discovery of the essential fatty acids (EFA), the symptoms of their deficiency were thoroughly delineated. The mechanisms by which these symptoms were produced, however, and the intimate functions of these substances remained obscure for many years. Smedley-MacLean and Hume (1) considered that the EFA are involved in the formation of new cells, and a careful consideration of the deficiency symptoms commonly described in EFA deficiency reveals that most of them are related in some way to a failure of membrane synthesis or maintenance.

The production of the antibiotic patulin in a three phase fluidized bed reactor: II. Longevity of the biocatalyst

AbstractThe longevity of the enzyme system for the production of the antibiotic patulin by immobilized Penicillium urticae cells was studied in a three phase fluidized bed reactor. Calculation of the global rate of patulin production indicated that, if the cells were not allowed to grow, the production of patulin gradually declined and stopped at 320 h. Intermittent pulse additions of nutrients stimulated the slow growth of the cells and resulted in an extended production time of 525 h. This long term production was the result of the formation of new cells rather than the maintenance of the original ones.

Ultrastructure of the corallinaceae. I. The vegetative cells of Corallina officinalis and C. cuvierii

A technique utilizing combined fixation and gentle decalcification has been employed to study the ultrastructure of the vegetative cells of the articulated calcareous coralline algae Corallina officinalis Linnaeus and C. cuvierii Lamouroux (Rhodophyta: Cryptonemiales). The epidermal cells are distinctive, with many cell wall inggrowths which pass between the chloroplasts. It is suggested that these cells function as “transfer cells”. The epidermal cells contain no starch, although the chloroplasts have well developed photosynthetic lamellae. Damage to these epidermal cells leads to formation of new cells by renewed division of sub-epidermal meristematic cells. The outer cortical cells have few small vacuoles and many plastids, with an extensive photosynthetic lamellar system. Deeper into the thallus, the vacuoles increase in size and free cytoplasmic starch grains occur. The medullary cells have a very large vacuole and in older tissue often appear dead. The long genicular cells have calcareous walls at either end while the wall in the middle of these cells is non-calcareous and has an inner fibrillar layer and a thin outer “cuticle”. In partially decalcified material, the orientation of the CaCO3 (calcite) crystals next to the cells can clearly be seen. Immediately next to the cell the crystals are fairly small and arranged at right angles to the plasmalemma. Further away from the cell the crystal size is larger and their orientation is more random. The crystals are surrounded by organic material, and the possible role of this material in calcification in coralline algae is discussed.

Mobilization of reserve lipids in germinating spores of the fern Anemia phyllitidis l.

Dry spores of Anemia phyllitidis contain 56% lipids of which 86% are triglycerides. The major fatty acids of these triglycerides are oleic and linoleic acid. During the spore germination process the triglycerides are being mobilized. The formation of new cells is correlated with an increase in the synthesis of phospholipids which are rich in linolenic acid.

Polyunsaturated fatty acid metabolism in neuroblastoma cells in culture.

Abstract—Neuroblastoma cell cultures took up linoleic and linolenic acids at approximately equal rates, and incorporated them into a variety of lipid fractions, principally cellular phospholipids. Linoleic acid was preferentially incorporated into choline phosphoglycerides, while most of the radioactivity derived from linolenic acid entered ethanolamine phosphoglycerides. There was no evidence for direct transfer of fatty acids between these two phosphoglyceride fractions. When, after the addition of cytosine arabinoside, cell division was arrested, the entry of labelled fatty acids into ethanolamine and serine phosphoglycerides was reduced, suggesting that these lipids are involved in the formation of new cell membranes.In the ethanolamine phosphoglyceride fraction, phosphatidal ethanolamine (plasmalogen) was the principal acceptor for the higher polyunsaturated fatty acids of the φ 3 series. The ratio of labelled fatty acids entering ethanolamine plasmalogens to that entering ethanolamine phosphoglycerides increased following the addition of cytosine arabinoside, suggesting plasmalogens to be involved in formation of cell processes.The first step in the metabolism of both linoleic and linolenic acid was the addition of a two‐carbon unit. Conversion of linoleic acid to higher polyunsaturated fatty acids was slower than the conversion of linolenic acid to its higher analogues. This contrasted with the behaviour of dissociated cultures of normal brain cells which were able to form higher analogues of linoleic and linolenic acids at nearly equal rates.

Predicted spacings in hydrogen-oxygen-argon detonations

A criterion for predicting the transverse spacing dimensions in gas phase detonations is developed. The criterion depends upon the collision of wave fronts to form new reaction centers which eventually lead to the formation of new cells. Calculated values of transverse spacing over a wide range of pressure, dilution and degree of overdrive in the hydrogen-oxygen-argon system are compared to experimental data for stoichiometric mixtures. The predicted values of spacing with no overdrive are about twice the experimental values. A minimum in the predicted spacing is found with overdrive as well as a cutoff value of overdrive for which the predicted spacing becomes infinite.