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PubMed2005

Short term exposure to 1439 MHz pulsed TDMA field does not alter melatonin synthesis in rats.

The widespread use of the mobile phone has initiated many studies on the possible adverse effects of a high frequency electromagnetic field (EMF), which is used in mobile phones. A low frequency EMF is reported to suppress melatonin synthesis. The aim of this study was to clarify the effects on melatonin synthesis in rats after short term exposure to a 1439 MHz time division multiple access (TDMA) EMF. The average specific absorption ratio (SAR) of the brain was 7.5 W/kg, and the average SARs of the whole body were 1.9 and 2.0 W/kg for male and female rats, respectively. A total of 208 male and female rats were investigated. After acclimatization to a 12 h light-dark (LD) cycle, serum and pineal melatonin levels together with pineal serotonin level under a dark condition (less than 1 lux) were examined by radioimmunoassay. No significant differences in melatonin and serotonin levels were observed between the exposure, sham, and cage control groups. These results suggest that short term exposure to a 1439 MHz TDMA EMF, which is about four times stronger than that emitted by mobile phones, does not alter melatonin and serotonin synthesis in rats. Further investigations on the effects of long term exposure are warranted.

Animals↗
PubMed2005

Bioprocess intensification in flow-through monolithic microbioreactors with immobilized bacteria.

Microporous polymers (with porosity up to 90%) with a well-prescribed internal microstructure were prepared in monolithic form to construct a flow-through microbioreactor in which phenol-degrading bacteria, Pseudomonas syringae, was immobilized. Initially, bacteria was forced seeded within the pores and subsequently allowed to proliferate followed by acclimatization and phenol degradation at various initial substrate concentrations and flow rates. Two types of microporous polymer were used as the monolithic support. These polymers differ with respect to their pore and interconnect sizes, macroscopic surface area for bacterial support, and phase volume. Polymer with a nominal pore size of 100 microm with phase volume of 90% (with highly open pore structure) yielded reduced bacterial proliferation, while the polymer with nominal pore size of 25 microm with phase volume of 85% (with small interconnect size and large pore area for bacterial adhesion) yielded monolayer bacterial proliferation. Bacteria within the 25 microm polymer support remained monolayered, without any apparent production of extracellular matrix during the 30-day continuous experimental period. The microbioreactor performance was characterized in terms of volumetric utilization rate and compared with the published data, including the case where the same bacteria was immobilized on the surface of microporous polymer beads and used in a packed bed during continuous degradation of phenol. It is shown that at similar initial substrate concentration, the volumetric utilization in the microreactor is at least 20-fold more efficient than the packed bed, depending on the flow rate of the substrate solution. The concentration of the bacteria within the pores of the microreactor decreases from 2.25 cells per microm2 on the top surface to about 0.4 cells per microm2 within 3 mm reactor depth. If the bacteria-depleted part of the microreactor is disregarded, the volumetric utilization increases by a factor of 30-fold compared with the packed bed. This efficiency increase is attributed to the reduction of diffusion path for the substrate and nutrients and enhanced availability of the bacteria for bioconversion in the absence of biofilm formation as well as the presence of flow over the surface of the monolayer bacteria.

Bioreactors↗
PubMed2007

Kinetics of biodegradation of p-xylene and naphthalene and oxygen transfer in a novel airlift immobilized bioreactor.

The scope of this study included the biodegradation performance and the rate of oxygen transfer in a pilot-scale immobilized soil bioreactor system (ISBR) of 10-L working volume. The ISBR was inoculated with an acclimatized population of contaminant degrading microorganisms. Immobilization of microorganisms on a non-woven polyester textile developed the active biofilm, thereby obtaining biodegradation rates of 81 mg/L x h and 40 mg/L x h for p-xylene and naphthalene, respectively. Monod kinetic model was found to be suitable to correlate the experimental data obtained during the course of batch and continuous operations. Oxygen uptake and transfer rates were determined during the batch biodegradation process. The dynamic gassing-out method was used to determine the oxygen uptake rate (OUR) and volumetric oxygen mass transfer, K(L) a. The maximum volumetric OUR of 255 mg O(2)/L x h occurred approximately at 720-722 h after inoculation, when the dry weight of biomass concentration was 0.67 g/L.

Biodegradation, Environmental↗
PubMed1994

Oxygen free radical activity in experimental colonic carcinoma.

Oxygen free radical activity has been implicated in carcinogenesis through DNA lysis. This study measured chemiluminescence and superoxide dismutase (SOD) inhibition as an index of oxygen free radical activity in azoxymethane-induced colonic carcinoma. After 3 weeks of acclimatization, ten Fisher 344 rats were injected with azoxymethane (7 mg kg-1 week-1) over 10 weeks. All animals were killed at 37 weeks and colonic mucosa (5-25 mg wet weight) was sampled from sites of histologically confirmed gross tumour and sites 3-5 cm distant from tumour as well as from ten paired normal controls. The samples were processed in buffered luminol and chemiluminescence was measured in a luminometer. Each sample was then placed in a solution of SOD for 3 min before a second chemiluminescence estimation. Mean(s.e.m.) chemiluminescence from control mucosal samples decreased from 8.1(1.0) to 3.9(1.1) mV per 100 mg tissue (P < 0.05) after incubation in SOD, suggesting that oxygen free radical activity was being measured. There was an increase to 20.2(0.9) mV per 100 mg in azoxymethane-treated colon remote from tumour and to 53.9(2.1) mV per 100 mg at tumour sites; both were reduced significantly after incubation with SOD to 6.7(0.7) and 11.0(0.8) mV per 100 mg respectively (P < 0.001). Chemiluminescence was significantly increased in azoxymethane-induced colonic carcinoma, both remote from and maximally at the tumour site, suggesting a field change in carcinogenesis associated with oxygen free radical activity.

Animals↗
PubMed1978

Female mouse maturation: effects of excreted and bladder urine from juvenile and adult males.

A sequence of 4 experiments examined the effects of prepubertal and adult males on the sexual maturation of young female house mice. The results support 3 conclusions: (1) the presence of a prepubertal male or of urine from prepubertal males does not affect the timing of sexual maturation in young female house mice; (2) the maturation-accelerating pheromone produced by adult males is present in the bladder urine of intact adult males but is absent from both excreted and bladder urine of castrated males; and (3) young females caged with 7 prepubertal males or with a castrated adult male mature earlier than control females caged alone. Results indicating that the presence of a castrated male leads to earlier sexual maturation of young female mice differ from previous findings. A possible explanation for this contradictory result is based on the ability of young weanling female mice to acclimatize the thermoregulate when separated from the dam and litter-mates. A model for density-feedback population regulation in house mice involving pheromones produced by males and females is presented.

Age Factors↗
PubMed2026

The Multiple Roles of Genetics on Freshwater Macrophyte Functional Traits in the Interplay With the Environment: A Review.

The study of functional trait variation is increasingly used to understand macrophyte adaptation, as traits reflect organismal performance under different ecosystem conditions. Phenotypic expression results from the interplay of genetic and environmental factors: genetics provides the molecular basis for heritable traits and constrains potential phenotypes, while the environment acts as a selective and modulatory force. However, the genetic insight into traits has rarely been addressed in freshwater macrophyte studies. This review examines the different ways in which the DNA of macrophytes interplays with the environment and contributes to the variation in their functional traits, outlining main approaches, gaps, and future challenges. Only 21 studies explicitly combined genetics with functional traits and environment in the last fifteen years. The most common approach was the use of common garden experiments to explore acclimation and adaptation in a few model species. Current studies mainly focus on morphological and growth traits that best describe macrophytes' economic strategies, with limited attention to other trait categories, while the genetic and DNA traits studied are more variable. Across studies, environmental factors generally explained a larger proportion of functional trait variation, highlighting the dominant role of phenotypic plasticity for macrophyte acclimatation, whereas genetic contribution increased under experimentally manipulated conditions. Genome size and epigenetic variation influenced phenotypic plasticity; however, the effect was different and inconsistent on traits and depended on phylogenetic relationships and geographical environment variation. In field studies of natural populations, life history traits and hydrology had a strong effect on the geographic distribution of genetic diversity and the response to selection, as well as on our ability to distinguish selection from genetic drift. Future research should enhance molecular analyses, adopt multifactorial and long-term experimental designs, develop conceptual frameworks to address the relationships between genomics, environment and functional traits and integrate emerging tools to capture macrophyte adaptation better.

adaptation↗
PubMed1994

Availability of calcium from kilkeerai (Amaranthus tricolor) and drumstick (Moringa oleifera) greens in weanling rats.

The present study was undertaken to determine the extent of calcium absorption in weanling rats from two types of greens rich in oxalates. The edible portions of greens namely kilkeerai (Amaranthus tricolor) and drumstick (Moringa oleifera) were analysed for moisture, calcium and total and soluble oxalates. Three groups of 6 male weanling albino rats were fed ad libitum on milk diet and two experimental diets containing greens. Urine and faecal samples were collected for a period of 7 days after 5 days of acclimatization period and were analysed for calcium. From the values obtained percent absorption and retention of calcium were calculated. Results revealed that calcium absorption and retention from milk diet (92 and 78%, respectively) were significantly higher than greens. Average calcium absorption and retention from greens diet were 75.5 and 60%, respectively. Presence of oxalates inhibited intestinal absorption of calcium.

Animals↗
PubMed2006

Effects of hypoxia on human mesenchymal stem cell expansion and plasticity in 3D constructs.

Low oxygen tension is thought to be an integral component of the human mesenchymal stem cell (hMSC) native bone marrow microenvironment. HMSC were cultured under physiologically relevant oxygen environments (2% O2) in three-dimensional (3D) constructs for up to 1 month in order to investigate the combined effects of chronic hypoxia and 3D architecture on hMSC tissue-development patterns. Hypoxic hMSC exhibited an extended lag phase in order to acclimatize to culture conditions. However, they subsequently proliferated continuously throughout the culture period, while maintaining significantly higher colony-forming unit capabilities and expressing higher levels of stem cell genes than hMSC cultured at 20% O2 (normoxic) conditions. Upon induction, hypoxic hMSC also expressed higher levels of osteoblastic and adipocytic differentiation markers than normoxic controls. Hypoxia induced increased total protein levels in hMSC throughout the culture period, as well as significantly different fibronectin expression patterns suggesting that oxygen levels can significantly affect tissue-development patterns. Importantly, hMSC maintained the ability to thrive in prolonged hypoxic conditions suggesting that hypoxia may be an essential element of the in vivo hMSC niche. Further studies are required to determine how variations in cellular characteristics and ECM expression impact on the physiological properties of the engineered tissue, yet these results strongly indicate that oxygen tension is a key parameter that influences the in vitro characteristics of hMSC and their development into tissues.

Adult↗
PubMed2002

Gene expression in peripheral arterial chemoreceptors.

The peripheral arterial chemoreceptors of the carotid body participate in the ventilatory responses to hypoxia and hypercapnia, the arousal responses to asphyxial apnea, and the acclimatization to high altitude. In response to an excitatory stimuli, glomus cells in the carotid body depolarize, their intracellular calcium levels rise, and neurotransmitters are released from them. Neurotransmitters then bind to autoreceptors on glomus cells and postsynaptic receptors on chemoafferents of the carotid sinus nerve. Binding to inhibitory or excitatory receptors on chemoafferents control the electrical activity of the carotid sinus nerve, which provides the input to respiratory-related brainstem nuclei. We and others have used gene expression in the carotid body as a tool to determine what neurotransmitters mediate the response of peripheral arterial chemoreceptors to excitatory stimuli, specifically hypoxia. Data from physiological studies support the involvement of numerous putative neurotransmitters in hypoxic chemosensitivity. This article reviews how in situ hybridization histochemistry and other cellular localization techniques confirm, refute, or expand what is known about the role of dopamine, norepinephrine, substance P, acetylcholine, adenosine, and ATP in chemotransmission. In spite of some species differences, review of the available data support that 1). dopamine and norepinephrine are synthesized and released from glomus cells in all species and play an inhibitory role in hypoxic chemosensitivity; 2). substance P and acetylcholine are not synthesized in glomus cells of most species but may be made and released from nerve fibers innervating the carotid body in essentially all species; 3). adenosine and ATP are ubiquitous molecules that most likely play an excitatory role in hypoxic chemosensitivity.

Animals↗
PubMed1985

Thermoregulatory responses to photoperiod by kangaroo rats (Dipodomys ordii): influence of night lighting on nonshivering thermogenesis and resting metabolism.

The influence of photoperiod on resting oxygen consumption and nonshivering thermogenesis of winter-acclimatized kangaroo rats was determined by exposing freshly captured animals to 10-week controlled photoperiod treatments. Three treatments were employed: 1) long days (LD) = 16L:8D, 2) short days (SD) = 8L:16D, and 3) short days interrupted with 15 min light at midnight (SDL). Thermoneutral oxygen consumption was uninfluenced by treatment, and posttreatment values were not different from pretreatment values. Below thermoneutrality, mean values for oxygen consumption and norepinephrine(NE)-induced thermogenesis each were significantly greater in the SD group than they were in either the LD or SDL groups. Furthermore, oxygen consumption of LD and SDL groups, and NE-induced thermogenesis of LD and SDL groups were indistinguishable. Posttreatment oxygen consumption and NE-induced thermogenesis of the SD group were not different from pretreatment values. These results indicate that thermogenic capacities of kangaroo rats are strongly influenced by photoperiod. The similarities of responses by the LD and SDL groups indicate that the length of the dark period is of importance, and indirectly support suggestions that the pineal gland, through its nocturnal secretion of melatonin, may be involved in the transduction of photic information.

Animals↗
PubMed1989

Seasonal variation in freeze tolerance and ice content of the tree frog Hyla versicolor.

Freeze tolerance and ice content of Hyla versicolor showed pronounced variation between summer (June) and winter (December). Summer frogs survived freezing at -3 degrees C for up to 9 hr and ice accumulation up to 50% of their total body water. A time course of ice formation indicated that an equilibrium level was reached in approximately 15 hr. Thus, the lethal ice content was less than the equilibrium ice content for these conditions (63.1%). A second group was induced to enter an overwintering condition by holding them through the summer and then subjecting them to a progressive reduction in temperature and photoperiod for 2 months. These frogs survived freezing for 48 hr at -3 degrees C. Their equilibrium ice content at this temperature was significantly lower (52.5%) than comparably treated summer animals. In the winter acclimatized group, frozen frogs had substantially higher blood glucose levels than unfrozen frogs (22.7 mumol/ml vs. 1.33 mumol/ml), but glycerol levels were not elevated after freezing. Freezing frogs conditioned for overwintering at -7 degrees C resulted in a higher equilibrium ice content (62.6%), but none survived. It is evident that in preparation for overwintering, frogs reduce the amount of ice formed at a given subzero temperature, but there is little indication of a substantial change in the total amount of ice tolerated.

Animals↗
PubMed2003

Cl- absorption in European eel intestine and its regulation.

The intestinal epithelium of the euryhaline teleost fish, Anguilla anguilla, absorbs Cl(-) transepithelially. This gives rise to a negative transepithelial potential at the basolateral side of the epithelium and to a measured short circuit current. Cl(-) absorption occurs via bumetanide-sensitive Na(+)-K(+)-2Cl(-) cotransport, localized on the luminal membrane. The cotransport operates in parallel with a luminal K(+) conductance that recycles the ion into the lumen. Cl(-) leaves the cell across the basolateral membrane by way of Cl(-) conductance and presumably via a KCl cotransport. The driving force for this process is provided by the electrochemical sodium gradient across the plasma membrane, generated and maintained by the basolateral Na(+)-K(+)-ATPase. The resulting NaCl absorption process is active and enables marine fish to take up water, thereby compensating for water that was lost passively from the body. Fresh water acclimatized eel also absorb Cl(-) actively, although in smaller quantities, utilizing the same ion transport mechanisms as marine eels. This mechanism is basically the same as the model proposed for the thick ascending limb (cTAL). Cl(-) absorption is regulated by a number of cellular factors, such as HCO(3) (-), pH, Ca(2+), cyclic nucleotides, and cytoskeletal elements. It is sensitive to osmotic stress, and therefore is a good physiological model to study ion transport mechanisms that are activated when osmotic stress induces cell volume regulation. The activation of these various ion transport pathways is dependent on cellular transduction mechanisms in which phosphorylation events (mainly by PKC and MLCK for the hypertonic response) and cytoskeletal elements, either microfilaments or microtubules, seem to play key roles.

Absorption↗
PubMed1981

Ultrastructural changes accompanying the growth of isolated oligodendrocytes.

The changes in the ultrastructure of oligodendrocytes with time in culture were examined by transmission electron microscopy. Oligodendrocytes were isolated from ovine white matter and maintained in Dulbecco's modified Eagle's medium supplemented with 20% horse serum. One day after being placed in plastic culture dishes, most cells aggregate into clusters that do not attach to the surface for several days. Cells within these clusters form junctional complexes resembling gap junctions, their nuclear chromatin becomes uniformly dispersed, they are rich in polyribosomes, and their cytoplasm is less osmiophilic than oligodendrocytes in ovine white matter or cells fixed immediately after isolation. After several days in culture, the cells become attached to the plastic surface, chromatin once again becomes clumped beneath the nuclear membrane, rough endoplasmic reticulum accumulates within the cytoplasm and the cells extend long processes containing cytoplasmic organelles. From these observations, it appears that oligodendrocytes undergo a transient dedifferentiation during their recovery from the trauma of isolation, not unlike the central chromatolysis seen in neurons following axonal injury. After acclimatization to tissue culture conditions, isolated oligodendrocytes show many of the morphologic features seen in vivo and therefore offer a good model to study myelination.

Animals↗
PubMed2002

Randomized trial comparing primidone initiation schedules for treating essential tremor.

Early side effects are common when primidone is used to treat essential tremor, with as many as one-third of patients failing to tolerate the tablets. Lower doses can be prescribed initially using a suspension formulation. We suspected suspension initiation would result in fewer early side effects, allow better acclimatization, and improve compliance. Forty patients with essential tremor were randomized to begin primidone treatment using either 2.5 mg doses in the suspension form or 25 mg doses in the tablet form. Doses gradually increased over 3 weeks to 150 mg/day. This was a double-blind, double-dummy trial. Medication cessation due to side effects was designated the primary end-point. Four patients in the suspension group and two in the tablet group dropped out due to early side effects, resulting in a relative risk of 1.9 (95% confidence interval 0.4 to 9.2). Side effects in the first 48 hours of treatment were equally common, affecting seven subjects in each group. Treatment benefits were the same in both groups. We concluded that use of a very low initial dose and a graduated titration schedule in suspension formulation did not appear to improve primidone tolerability. If anything, compliance tended to be worse when compared with the tablet formulation, though the study was under-powered to reject the null hypothesis of equivalence.

Administration, Oral↗
PubMed1984

Effect of cigarette smoking on experimental microvascular anastomoses.

Cigarette smoking has been shown to cause cutaneous vasoconstriction, a decrease in digital blood flow, impaired wound healing, and it was implicated as a cause of failure of microvascular anastomoses in replanted digits. The subject of the following study was to assess the effect of cigarette smoking on experimental microvascular anastomoses. Twenty Sprague-Dawley male rats weighting 200 to 250 grams were divided into groups of ten. Both the experimental and the control groups were acclimatized to a Maddox/ORNL rat smoke inhalation exposure system for six days prior to operation. At this time they were anesthetized and bilateral femoral artery end to end anastomoses were performed by two surgeons, using standard microsurgical techniques. After a recovery period of 24 hours, both groups were started on a smoking/sham-smoking regime for 12 to 13 days. After this time they were anesthetized again, the femoral artery anastomoses were checked for patency in vivo and excised for histological evaluation. Five cm3 of blood was drawn from each animal to be analyzed for the presence of nicotine and its metabolites, and the rats were sacrificed. All the anastomoses in both groups were patent at the time of exploration and no histological difference could be demonstrated between the two groups. The radioimmunoassay of nicotine and cotinine showed large amounts in the smokers, and none in the nonsmokers.

Animals↗
PubMed2005

Stream macroinvertebrate drift response to pulsed exposure of the synthetic pyrethroid lambda-cyhalothrin.

Outdoor experimental channels were used to study the behavioral changes of stream macroinvertebrates exposed to a pulse of the pyrethroid insecticide lambda-cyhalothrin. The primary end point was the number of macroinvertebrates drifting, but the mobility of macroinvertebrates caught in the drift also was assessed. A specified number of two insect species, Baetis rhodani and Leuctra fusca/digitata, and of the amphipod Gammarus pulex were introduced into small replicated subsections of the experimental channels. Macroinvertebrates were allowed to acclimatize for 26 h prior to a 60-min pulsed exposure to lambda-cyhalothrin. Measurement was initiated 2 h before pesticide application and continued for the following 24 h. Pulse concentrations of lambda-cyhalothrin of 0.001, 0.01, 0.1, and 1.0 microg L(-1) were applied, and each experiment was replicated 8 times. All three species responded to the pesticide pulse with catastrophic drift. The 0.001 microg L(-1) treatment caused a significant increase in the drift of Gammarus, whereas the drift response threshold was 0.01 microg L(-1) for the two insect species. Drift response onset followed the applied pulse concentration, with the highest concentrations resulting in more individuals of all species entering drift at an early stage. The majority of individuals caught in drift samples during low concentrations showed no change in mobility. At the two highest concentrations, however, both Baetis and Leuctra were in the process of being immobilized, with Leuctra the more sensitive of the two. In contrast, only a few of the Gammarus individuals caught showed changes in mobility after the high-concentration treatments. The present study shows that lambda-cyhalothrin is a potential hazard for macroinvertebrate populations in headwater streams. The clear species-specific responses indicate that sublethal doses have the potential to change the macroinvertebrate community structure.

Amphipoda↗
PubMed1996

Accumulation and distribution of inorganic mercury in a tropical fish (Trichomycterus zonatus).

Different aspects of mercury accumulation, retention, and elimination in temperate fish species have been reported, but few data are available for tropical species. In this work Hg accumulation in Trichomycterus zonatus, where experimental losses were estimated, was studied. Forty individuals (males and females) of T. zonatus were acclimatized for 30 days. In each experiment 10 aquaria were used, with 1 fish each (5 exposed to HgCl2 and the others as controls). The concentration tested was 15 microg Hg x liter-1 including 18 kBq x liter-1 203HgCl2 as tracer. Fish were dissected and measured for Hg by gamma scintillation spectrometry at regular intervals, and after 96 hr were transferred to mercury-free tap water. Approximately 40% of added mercury was lost by volatilization (20%) and adsorption (20%) in 48 hr. A faster absorption of inorganic mercury was observed initially in gills, a higher and lower retention in kidney and muscle, respectively. For T. zonatus the kidney, gills, and liver were considered the critical organs, but this order changed after 98 hr in mercury-free tap water. The distribution of inorganic mercury in T. zonatus seems quite similar to that found in temperate species, but the sensitivity of this species to Hg seems higher.

Animals↗
PubMed1999

Combining life-history and toxicokinetic parameters to interpret differences in sensitivity to cadmium between populations of Polycelis tenuis (Platyhelminthes).

Five populations of the planarian Polycelis tenuis, collected from four locations in a metal contaminated stream and from one location in an unpolluted tributary stream, were compared for their sensitivity to cadmium by measuring survival, reproduction, and body size changes during 28 days of exposure via the water. Survival data and bioconcentration of cadmium measured at the end of the experiment enabled the use of a kinetic-based toxicity model, estimating the lethal body concentration, the uptake rate constant, the elimination rate constant, and the ultimate LC(50) as estimated toxicokinetic parameters. Accurate body size selection and a one-month acclimatization period to standardized laboratory conditions were applied to enhance the comparability between populations. An increased elimination rate constant and a greater ultimate LC(50) were estimated for one of the populations, located downstream from an ancient lead-zinc mine. The cadmium concentration causing an effect on reproduction varied considerably (a factor of 10) among populations but did not differ significantly between populations. For the number of reproducing individuals as a function of cadmium concentration, EC(50) and steepness of slope of the concentration/effect relationship tended to be correlated positively (P<0.10), indicating that selection in the field may have occurred. Cadmium was found to enhance shrinkage of P. tenuis under conditions of food limitation.

Animals↗