Behavioral and reproductive responses of female opossums to volatile and nonvolatile components of male suprasternal gland secretion

Female gray short-tailed opossums (Monodelphis domestica) lack an estrous cycle and are induced into estrus by exposure to a pheromone in male scent marks. Behavioral and physiological responses of females to the volatile and nonvolatile components of scent marks were examined in two experiments. Young females (n = 9) were tested prior to and during their first estrus for behavioral responses to scent marks, collected on a 7-ml glass vial rubbed over the suprasternal gland of a mature male. The response to volatile components of the scent mark, recorded when marked and unmarked vials were covered with a perforated shield, was compared to the response to these vials when unshielded. Estrous females nuzzled the shields over marked vials (55.8 ± 8.5 nuzzles/10 min) more than the shielded clean vial (10.9 ± 2.4) (P < 0.05); a similar response was observed in anestrous females. Nuzzling of unshielded, scent-marked vials was higher (P < 0.05) during anestrus than in the same females when in estrus. The role of nonvolatile pheromones in reproductive activation was tested in adult females (n = 11) exposed for up to 14 days to a shielded, marked vial or to an unshielded, marked vial in a crossover design. All females exposed to unshielded vials expressed estrus, and 10 copulated. Only 2 females expressed estrus (significantly fewer, P < 0.05), when exposed to shielded marked vials, and neither copulated. These results demonstrate that females detect and respond behaviorally to both volatile and nonvolatile components of male suprasternal gland secretion, but the estrus-inducing pheromone in these secretions is nonvolatile.     

Rheology of Mixed Pectin Solutions

The effects of sucrose (S) and pectin (P) concentrations and the ratio between two distinct pectins (R) on the rheological behavior of diluted pectin systems were evaluated simultaneously using the surface response methodology. The systems were composed of a mixture of two high methoxy pectins with different degree of methyl esterification values (HM1/HM2) and of a mixture of a high-methoxy with an amidated low-methoxy pectin (HM1/LMA). For the HM1/HM2 systems, the multivariate analysis showed that the sucrose and pectin concentrations exerted statistically significant (p < 0.05) linear effects on the consistency index k and viscosity, the influence of pectin being about five times higher than that of sucrose. The pectin concentration and the ratio between the different pectins were shown to be significant with respect to the rheological parameters of the HM1/LMA systems. Evaluating the influence of the ratio between the different pectins, a synergistic effect on the structure reinforcement was observed when mixing HM1 and LMA in similar proportions, indicating the importance of the presence of hydrophobic interactions between methyl ester groups in addition to the stronger hydrogen bonding in junction zone stabilization. In general, the conditions in which hydrogen bonds were favored in relation to hydrophobic interactions led to systems with higher pseudoplasticity.     

Comparison of the effects of cationic porphyrins on DNA properties: influence of GC content of native and synthetic polymers

Interactions of meso-tetra(4-N-methylpyridyl)porphyrin [TMpyP(4)], meso-tetra(2-N-methylpyridyl)porphyrin [TMpyP(2)], and meso-tetra(para-N-trimethylanilinium)porphyrin (TMAP) with several native and synthetic DNAs were studied by a variety of physical techniques: nmr (³¹P and ¹H), absorption spectroscopy, viscosity, and flow dichroism (FD). Of the three porphyrins studied, only the interaction of TMpyP(4) with poly [d(G-C)₂] was fully consistent with intercalation. In particular, a large increase in viscosity, a downfield ³¹P-nmr signal (ca. -1 ppm), and upfield imino proton signals (11 to 12 ppm range) were observed. Comparison of the effects of TMpyP(4) on DNAs of different GC contents revealed larger changes in solution viscosity with increased GC content. However, the characteristic changes in ³¹P- and ¹H-nmr spectra were not observed. The viscosity increases observed in studies with poly[d(A-C)(G-T)] and C. Perf. DNA were much lower than with poly[d(G-C)₂], M. Lys. DNA, and calf thymus DNA. Thus, GC sequence and content are clearly important. The principal change in the ³¹P-nmr signal of native DNA is the appearance of a very broad shoulder centered at ca. -2.0 ppm, which is larger in M. Lys. DNA than in C. Perf. DNA. FD studies indicate highly ordered TMpyP(4) cations arranged perpendicular to the DNA axis of calf thymus DNA. Together, these results suggest the major effects of TMpyP(4) on DNA properties are due to strong GC-binding interactions that influence DNA structure. The data are consistent with combined intercalative and outside binding interactions of TMpyP(4) with GC regions of DNA. In contrast, similar studies with TMAP suggest that it influences AT regions of DNA by an outside binding mode. On the other hand, TMpyP(2) effects on DNA properties are consistent with nonselective outside binding.     

Ad hoc instrumentation methods in ecological studies produce highly biased temperature measurements

In light of global climate change, ecological studies increasingly address effects of temperature on organisms and ecosystems. To measure air temperature at biologically relevant scales in the field, ecologists often use small, portable temperature sensors. Sensors must be shielded from solar radiation to provide accurate temperature measurements, but our review of 18 years of ecological literature indicates that shielding practices vary across studies (when reported at all), and that ecologists often invent and construct ad hoc radiation shields without testing their efficacy. We performed two field experiments to examine the accuracy of temperature observations from three commonly used portable data loggers (HOBO Pro, HOBO Pendant, and iButton hygrochron) housed in manufactured Gill shields or ad hoc, custom‐fabricated shields constructed from everyday materials such as plastic cups. We installed this sensor array (five replicates of 11 sensor‐shield combinations) at weather stations located in open and forested sites. HOBO Pro sensors with Gill shields were the most accurate devices, with a mean absolute error of 0.2°C relative to weather stations at each site. Error in ad hoc shield treatments ranged from 0.8 to 3.0°C, with the largest errors at the open site. We then deployed one replicate of each sensor‐shield combination at five sites that varied in the amount of urban impervious surface cover, which presents a further shielding challenge. Bias in sensors paired with ad hoc shields increased by up to 0.7°C for every 10% increase in impervious surface. Our results indicate that, due to variable shielding practices, the ecological literature likely includes highly biased temperature data that cannot be compared directly across studies. If left unaddressed, these errors will hinder efforts to predict biological responses to climate change. We call for greater standardization in how temperature data are recorded in the field, handled in analyses, and reported in publications.     

Trophic cul-de-sac, Pyrazus ebeninus, limits trophic transfer through an estuarine detritus-based food web

The importance to food‐webs of trophic cul‐de‐sacs, species that channel energy flow away from higher trophic levels, is seldom considered outside of the pelagic systems in which they were first identified. On intertidal mudflats, inputs of detritus from saltmarshes, macroalgae or microphytobenthos are generally regarded as a major structuring force underpinning food‐webs and there has been no consideration of trophic cul‐de‐sacs to date. A fully orthogonal three‐factor experiment manipulating the density of the abundant gastropod, Pyrazus ebeninus, detritus and macrobenthic predators on a Sydney mudflat revealed large deleterious effects of the gastropod, irrespective of detrital loading or the presence of predators. Two months after experimental manipulation, the standing‐stock of microphytobenthos in plots with high (44 per m²) densities of P. ebeninus was 20% less than in plots with low (4 per m²) densities. Increasing densities of P. ebeninus from low to high halved the abundance of macroinvertebrates and the average number of species. In contrast, the addition of detritus had differing effects on microphytobenthos (positively affected) and macroinvertebrates (negatively affected). Over the two‐months of our experiment, no predatory mortality of P. ebeninus was observed and high densities of P. ebeninus decreased impacts of predators on macroinvertebrate abundances. Given that the dynamics of southeast Australian mudflats are driven more by disturbance than seasonality in predators and their interactions with prey, it is likely that Pyrazus would be similarly resistant to predation and have negative effects on benthic assemblages at other times of the year, outside of our study period. Thus, in reducing microphytobenthos and the abundance and species richness of macrofauna, high abundances of the detritivore P. ebeninus may severely limit the flow of energy up the food chain to commercially‐important species. This study therefore suggests that trophic cul‐de‐sacs are not limited to the eutrophied pelagic systems in which they were first identified, but may exist in other systems as well.     

Steady-state viscosity of the liquid two-phase disperse system water-casein-sodium alginate

The steady-state viscosity (η^*) of the liquid two-phase disperse system water-casein-sodium alginate of varying composition, with a disperse particle diameter of about 30 μm, has been investigated in the shear rate range . The flow curves obtained are similar in shape. They are invariant in composition and can be fitted to the flow curve equation where η^*₀ is the Newtonian viscosity obtained from data at low shear stresses and k is an empirical parameter. Both η^*₀ and k depend on the composition of the two-phase system.The experimental dependence of the viscosity on the composition follows a logarithmic additivity law at high shear stresses, but at low shear stresses the observed viscosities are lower than would be predicted by this law. The experimental dependence of the ratio (the mean activation volume) on the composition is also not in agreement with the additivity law. These special features of the steady-state flow of the investigated disperse system are explained by the presence of a low-concentration interphase layer having a lower viscosity and less pronounced non-Newtonian behaviour than the disperse and continuous phases. This interphase layer exists in other two-phase systems which consist of a solvent and two incompatible polymers. For this reason, the rheological behaviour of the system investigated may be expected to be common for two-phase systems of this type, particularly protein-polysaccharide mixtures in water.     

Effects of embryonic responses to clutch mates on egg hatching patterns of Pentatomidae (Heteroptera)

Stink bugs and shield bugs of the family Pentatomidae (Heteroptera) generally produce a clutch of densely deposited eggs. In a few species of this family, embryos hatch in response to some form of cues associated with the preceding hatching to synchronize egg hatching with clutch mates. The aim of the present study is to obtain a family‐wide understanding of the extent to which the hatching response to clutch mates accelerates hatching within egg clutches. Accordingly, the hatching patterns in intact egg clutches and eggs individually detached from egg clutches are compared in eight species among different genera. In Halyomorpha halys, hatching is significantly and highly synchronized by the effect of the hatching response: when eggs are not attached to each other, the hatching rate is only 3.8% at 15 min and exceeds 95% at 200 min. By contrast, when eggs are attached to each other, the hatching rate reaches more than 95% at 15 min. Hatching is also significantly synchronized by the hatching response in Nezara viridula (which shows relatively high hatching synchronization) and in Piezodorus hybneri and Plautia stali (both of which show milder hatching synchronization). Synchronization of hatching is not found to be promoted by a hatching response in Aelia fieberi, Dolycoris baccarum, Eurydema rugosum or Palomena angulosa. These findings reveal that the hatching response varies depending on the species in Pentatomidae, with a wide spectrum of effects on the hatching patterns of the egg clutches.     

Luminescence Spectroscopy – a Useful Tool in Real-Time Monitoring of Viscosity during In-Vitro Digestion

Luminescence spectroscopy coupled with molecular rotors was used in the TNO Intestinal Model-1 (TIM-1) to monitor in situ changes to luminal viscosity of three maize starch samples varying in the amylose-to-amylopectin ratio (AM: AP): normal, high amylose (AM) and high amylopectin (AP). The fluorescence intensity (FI) of Fast Green (FG), a proven micro (and bulk) viscosity probe, was monitored throughout digestion to track changes in the gastric viscosity. The FI of FG and the viscosity imparted by the starch followed a power-law relationship. The emission of the MR was unaffected by the composition of TIM-1 secretion fluids nor pH. Hence, direct measurements of digesta FI are sensitive to changing viscosity during the simulated digestion. The viscosity was highest for AP, followed by normal starch, and high AM had the lowest viscosity. In the TIM-1 gastric compartment, from highest to lowest FI, and thus viscosity was high AM > high AP > normal maize starches. We conclude the validity of the proposed method to facilitate the measurement of luminal viscosity, in vitro, when the microviscosity represents bulk viscosity (i.e., when the increase in bulk viscosity is a result of molecular crowding and the surrounding environment around the rotor is homogeneous). Careful consideration is required when foods are heterogeneous as molecular rotors report only on their local non-uniform environment.

     

A plethysmographic technique for direct measurement of airway resistance in hamsters

We have developed a new technique to directly measure airway resistance (Raw) in small animals with a pressure-type body plethysmograph equipped with a hot-wire microflow sensor. Seventeen male golden hamsters weighing 70-84 g were studied. Change in alveolar pressure (delta PA) was calculated from total gas volume and the respired volume difference through the flow sensor between the midpoints of the tidal excursion curve, reflecting the thorax movement. The ratio of delta PA to the flow difference between those two midpoints gave Raw. Raw was compared with pulmonary resistance, and inspiratory and expiratory resistances were also compared. Raw was 0.44 +/- 0.06 (SE) cmH2O.ml-1.s. Mean of the coefficients of variation of Raw was 19.6 +/- 3.2% (SE). Raw was well correlated with pulmonary resistance (r = 0.93). We demonstrated that Raw could be directly measured in small animals with a hot-wire flow sensor and a plethysmographic technique, and the values were well correlated with previously reported pulmonary resistance.     

Hemorheological implications of perfluorocarbon based oxygen carrier interaction with colloid plasma expanders and blood

Perfluorocarbon (PFC) emulsions used as artificial oxygen carriers lack colloid osmotic pressure (COP) and must be administered with colloid‐based plasma expanders (PEs). Although PFC emulsions have been widely studied, there is limited information about PFC emulsion interaction with PEs and blood. Their interaction forms aggregates due to electrostatic and rheological phenomena, and change blood rheology and blood flow. This study analyzes the effects of the interaction between PFC emulsions with blood in the presence of clinically‐used PEs. The rheological behavior of the mixtures was analyzed in vitro in parallel with in vivo analysis of blood flow in the microcirculation using intravital microscopy, when PEs were administered in a clinically relevant scenario. The interaction between the PFC emulsion and PE with blood produced PFC droplets and red blood cell (RBCs) aggregation and increased blood viscosity in a shear dependent fashion. The PFC droplets formed aggregates when mixed with PEs containing electrolytes, and the aggregation increased with the electrolyte concentration. Mixtures of PFC with PEs that produced PFC aggregates also induced RCBs aggregation when mixed with blood, increasing blood viscosity at low shear rates. The more viscous suspension at low shear rates produced a blunted blood flow velocity profile in vivo compared to nonaggregating mixtures of PFC and PEs. For the PEs evaluated, human serum albumin produced minimal to undetectable aggregation. PFC and PEs interaction with blood can affect sections of the microcirculation with low shear rates (e.g., arterioles, venules, and pulmonary circulation) when used in a clinical setting, because persistent aggregates could cause capillary occlusion, decreased perfusion, pulmonary emboli or focal ischemia. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29:796–807, 2013     

FLOW PATTERN AROUND THE RIGID CEPHALIC SHIELD OF THE DEVONIAN AGNATHAN ERRIVASPIS WAYNENSIS (PTERASPIDIFORMES: HETEROSTRACI)

Abstract: Palaeozoic armoured agnathans (or ostracoderms) are characterised by having an external, bone shield enclosing the anterior part of their bodies, which demonstrate great diversity of both forms and sizes. The functional significance of these cephalic shields remains unclear (they may have been a functional analogue of the vertebral column, or merely afforded protection). Here we assess the importance of the cephalic shield in terms of locomotion. In order to do this, we have studied flow patterns of the Devonian heterostracan Errivaspis waynensis ( White, 1935 ), using an anatomically correct model of E. waynensis positioned at different pitching angles. The fluid flow was visualised in a wind tunnel, using planar light sheet techniques, adding vaporised propylene glycol to the fluid. The flow pattern over the cephalic shield of Errivaspis is dominated by the formation of leading‐edge vortices (LEVs). When the model was positioned at angles of attack of ‐2 degrees or higher a pair of nearly symmetrical, counter‐rotating primary vortices were produced, which flowed downstream over the upper surface of the cephalic shield. At moderate angles of attack, LEVs remained attached to the dorsal surface, but, as the angle of attack increased above 7 degrees, vortices began to separate from the surface at posterior locations. At a high angles of attack (around 12 degrees or 13 degrees), vortex breakdown (or vortex burst) occured. The body‐induced vortical flow around the cephalic shield is very similar to the that described over delta wing aircraft. This strategy generates lift forces through vortex generation (vortex lift). Based on this analogue and knowing that Errivaspis lacked pectoral fins or any other obvious control surfaces, vortex lift forces added through this mechanism may have played a major role in the locomotion of these primitive fishes, not only to counteract the negative buoyancy of the fish, but also as a means of manoeuvring.     

The role of epidermal turgor in stomatal interactions following a local perturbation in humidity

Humidity in a small area of a Vicia faba L. leaf was perturbed with a flow of dry air from an 80 µm (inside diameter) needle, while the remainder of the leaf was maintained at high and constant humidity. The influence of the needle flow on the humidity at the leaf surface was quantified by using a spatially explicit dewpoint hygrometer to observe condensation patterns. When the dry air from a needle was applied to the leaf, stomata within the influence of the needle opened within the first few minutes of the perturbation, and local epidermal turgor pressure declined within the same time frame. When the needle flow was removed from the leaf, these responses were reversed, but with more variable kinetics. Stomata and epidermal cells outside the influence of the needle flow, which were exposed to a constant and high humidity, showed similar, but smaller, responses when the needle flow was applied to the leaf. Since the opening of these stomata should have had only a small effect on transpiration (because of the high humidity), it is likely that the reduction in epidermal turgor was the cause (rather than the result) of the stomatal opening. The magnitude of the turgor response was only loosely related to the distance from the needle flow up to distances of almost 400 µm. The data support the idea that neighbouring stomata can interact through the influence of transpiration on epidermal turgor.     

MICROSATELLITES REVEAL HIGH POPULATION VISCOSITY AND LIMITED DISPERSAL IN THE ANT FORMICA PARALUGUBRIS

We used microsatellites to study the fine-scale genetic structure of a highly polygynous and largely unicolonial population of the ant Formica paralugubris. Genetic data indicate that long-distance gene flow between established nests is limited and new queens are primarily recruited from within their natal nest. Most matings occur between nestmates and are random at this level. In the center of the study area, budding and permanent connections between nests result in strong population viscosity, with close nests being more similar genetically than distant nests. In contrast, nests located outside of this supercolony show no isolation by distance, suggesting that they have been initiated by queens that participated in mating flights rather than by budding from nearby nests in our sample population. Recruitment of nestmates as new reproductive individuals and population viscosity in the supercolony increase genetic differentiation between nests. This in turn inflates relatedness estimates among worker nestmates (r = 0.17) above what is due to close pedigree links. Local spatial genetic differentiation may favor the maintenance of altruism when workers raise queens that will disperse on foot and compete with less related queens from neighboring nests or disperse on the wing and compete with unrelated queens.     

The auxiliary protein complex SaePQ activates the phosphatase activity of sensor kinase SaeS in the SaeRS two‐component system of Staphylococcus aureus

In bacterial two‐component regulatory systems (TCSs), dephosphorylation of phosphorylated response regulators is essential for resetting the activated systems to the pre‐activation state. However, in the SaeRS TCS, a major virulence TCS of Staphylococcus aureus, the mechanism for dephosphorylation of the response regulator SaeR has not been identified. Here we report that two auxiliary proteins from the sae operon, SaeP and SaeQ, form a protein complex with the sensor kinase SaeS and activate the sensor kinase's phosphatase activity. Efficient activation of the phosphatase activity required the presence of both SaeP and SaeQ. When SaeP and SaeQ were ectopically expressed, the expression of coagulase, a sae target with low affinity for phosphorylated SaeR, was greatly reduced, while the expression of alpha‐haemolysin, a sae target with high affinity for phosphorylated SaeR, was not, demonstrating a differential effect of SaePQ on sae target gene expression. When expression of SaePQ was abolished, most sae target genes were induced at an elevated level. Since the expression of SaeP and SaeQ is induced by the SaeRS TCS, these results suggest that the SaeRS TCS returns to the pre‐activation state by a negative feedback mechanism.     

Marine hydrocarbonoclastic bacteria as whole‐cell biosensors for n‐alkanes

Whole‐cell biosensors offer potentially useful, cost‐effective systems for the in‐situ monitoring of seawater for hydrocarbons derived from accidental spills. The present work compares the performance of a biosensor system for the detection of alkanes in seawater, hosted in either Escherichia coli (commonly employed in whole‐cell biosensors but not optimized for alkane assimilation) or different marine bacteria specialized in assimilating alkanes. The sensor system was based on the Pseudomonas putida AlkS regulatory protein and the PalkB promoter fused to a gene encoding the green fluorescent protein. While the E. coli sensor provided the fastest response to pure alkanes (25‐fold induction after 2 h under the conditions used), a sensor based on Alcanivorax borkumensis was slower, requiring 3–4 h to reach similar induction values. However, the A. borkumensis sensor showed a fourfold lower detection threshold for octane (0.5 μM), and was also better at sensing the alkanes present in petrol. At petrol concentrations of 0.0125%, the A. borkumensis sensor rendered a sevenfold induction, while E. coli sensor showed no response. We discuss possible explanations to this behaviour in terms of the cellular adaptations to alkane uptake and the basal fluorescence produced by each bacterial strain, which was lowest for A. borkumensis.     

Expression,purification and activities of the entire family of intact membrane sensor kinases from Enterococcus faecalis

Two-component signal transduction systems are the main mechanism by which bacteria sense and respond to their environment, and their membrane-located histidine protein kinases generally constitute the sensory components of these systems. Relatively little is known about their fundamental mechanisms and precise nature of the molecular signals sensed, because of the technical challenges of producing sufficient quantities of these hydrophobic membrane proteins. This study evaluated the heterologous production, purification and activities of the 16 intact membrane sensor kinases of Enterococcus faecalis. Following the cloning of the genes into expression plasmid pTTQ18His, all but one kinase was expressed successfully in Escherichia coli inner membranes. Purification of the hexa-histidine ‘tagged’ recombinant proteins was achieved for 13, and all but one were verified as intact. Thirteen intact kinases possessed autophosphorylation activity with no added signal when assayed in membrane vesicles or as purified proteins. Signal testing of two functionally-characterized kinases, FsrC and VicK, was successful examplifying the potential use of in vitro activity assays of intact proteins for systematic signal identification. Intact FsrC exhibited an approximately 10-fold increase in activity in response to a two-fold molar excess of synthetic GBAP pheromone, whilst glutathione, and possibly redox potential, were identified for the first time as direct modulators of VicK activity in vitro. The impact of DTT on VicK phosphorylation resulted in increased levels of phosphorylated VicR, the downstream response regulator, thereby confirming the potential of this in vitro approach for investigations of modulator effects on the entire signal transduction process of two-component systems.     

Behavioral and reproductive responses of female opossums to volatile and nonvolatile components of male suprasternal gland secretion

Female gray short-tailed opossums (Monodelphis domestica) lack an estrous cycle and are induced into estrus by exposure to a pheromone in male scent marks. Behavioral and physiological responses of females to the volatile and nonvolatile components of scent marks were examined in two experiments. Young females (n = 9) were tested prior to and during their first estrus for behavioral responses to scent marks, collected on a 7-ml glass vial rubbed over the suprasternal gland of a mature male. The response to volatile components of the scent mark, recorded when marked and unmarked vials were covered with a perforated shield, was compared to the response to these vials when unshielded. Estrous females nuzzled the shields over marked vials (55.8 ± 8.5 nuzzles/10 min) more than the shielded clean vial (10.9 ± 2.4) (P < 0.05); a similar response was observed in anestrous females. Nuzzling of unshielded, scent-marked vials was higher (P < 0.05) during anestrus than in the same females when in estrus. The role of nonvolatile pheromones in reproductive activation was tested in adult females (n = 11) exposed for up to 14 days to a shielded, marked vial or to an unshielded, marked vial in a crossover design. All females exposed to unshielded vials expressed estrus, and 10 copulated. Only 2 females expressed estrus (significantly fewer, P < 0.05), when exposed to shielded marked vials, and neither copulated. These results demonstrate that females detect and respond behaviorally to both volatile and nonvolatile components of male suprasternal gland secretion, but the estrus-inducing pheromone in these secretions is nonvolatile.     

Microbial corrosion monitoring by an amperometric microbial biosensor developed using whole cell of Pseudomonas sp.

A microbial biosensor was developed for monitoring microbiologically influenced corrosion (MIC) of metallic materials in industrial systems. The Pseudomonas sp. isolated from corroded metal surface was immobilized on acetylcellulose membrane and its respiratory activity was estimated by measuring oxygen consumption. The microbial biosensor was used for the measurement of sulfuric acid in a batch culture medium contaminated by microorganisms. A linear relationship between the microbial sensor response and the concentration of sulfuric acid was observed. The response time of biosensor was 5 min and was dependent on the immobilized cell loading of Pseudomonas sp., pH, temperature and corrosive environments. The microbial biosensor response was stable, reproducible and specific for sensing of sulfur oxidizing bacterial activity.     

Cell-cycle kinetics of friend erythroleukemia cells in a magnetically shielded room and in a low-frequency/low-intensity magnetic field

This work was undertaken to compare the behavior of Friend erythroleukemia cells in a solenoid, where the magnetic field was 70 μT at 50 Hz (plus 45 μT DC of Earth) with that of the same cells in a magnetically shielded room, where the magnetic field was attenuated to 20 nT DC and 2.5 pT AC. The control laboratory magnetic field corresponded to 45 μT DC and a stray 50 Hz field below 0.2 μT. The culture growth cycle of cells maintained inside the solenoid was slightly accelerated compared with that of cells maintained outside the solenoid (P < .05). This stimulation probably depended on sensitivity of cell cycle to a magnetic field, because, inside the solenoid, the percentage of G₁ cells slightly increased during the culture growth cycle, whereas that of S cells slightly decreased. Acceleration of growth was detected soon after exposure of the cultures to the solenoid field, and growth did not change further if the action of this field continued for a long time, accounting for adaptation. The solenoid field also caused a small increase of cell survival without influencing cell volume. By contrast, the culture growth cycle of cells maintained inside the magnetically shielded room was slightly decelerated compared with that of cells maintained outside the room (P < .05). The essential absence of any field inside the magnetically shielded room also caused a small increase of cell volume, whereas, during the culture growth cycle, the percentage of G₁ cells decreased, and that of S cells increased. The majority of these events did not change in cells induced to differentiate hemoglobin through dimethylsulfoxide. Bioelectromagnetics 18:58–66, 1997. © 1997 Wiley-Liss, Inc.