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At least 235 records · Page 13Linked to original sources
PubMed2006

Some vaguely explored (but not trivial) costs of tail autotomy in lizards.

Lizard tail autotomy is considered an efficient anti-predator strategy that allows animals to escape from a predator attack. However, since the tail also is involved in many alternative functions, tailless animals must cope with several costs following autotomy. Here we explicitly evaluate the consequences of tail autotomy for two costs that have been virtually unexplored: 1. we test whether the anatomical change that occurs after tail loss causes a reduction in the role of the tail as a distraction mechanism to predators; 2. we analyzed whether tail synthesis comprises an energetically costly process in itself, by directly comparing the cost of maintenance before and after autotomy. We found that original tails displace further and at greater velocity than regenerated tails, indicating that the anti-predation responses of a lizard probably changes according to whether its tail is original or regenerated. With regard to the energetic cost of tail synthesis, we observed a significant increase in the standard metabolic rate, which rose 36% in relation to the value recorded prior to tail loss. This result suggests that the energetic cost of tail synthesis itself could be enough to affect lizard fitness.

Animals↗
PubMed2002

Toxicity of cadmium and zinc to cercarial tail loss in Diplostomum spathaceum (Trematoda: Diplostomidae).

The effect of cadmium and zinc at concentrations ranging from 0.1 to 10,000 microg/l on tail loss in cercariae of Diplostomum spathaceum was investigated at 3 temperatures (12, 20 and 25 degrees C) and 3 levels of water hardness (distilled water, soft water and hard water). Increasing tail loss over time was found to be linked with a parallel decrease in cercarial survival in controls. Exposure to the heavy metals induced, especially at high concentrations, a change in the relationship between cercarial tail loss and survival, causing either stimulation or inhibition of tail loss dependent on the individual toxic exposure. Under most environmental conditions the rate of tail loss over time was reduced by increasing metal concentrations. Inhibition of tail loss occurred in a limited number of both control and metal-exposed cercariae, with a number of low metal concentrations inducing greater inhibition than in controls. Stimulation of tail loss causing an increased tail loss rate above controls also occurred at certain high metal concentrations. Increasing water hardness and decreasing water temperature caused a reduced tail loss rate over time in both control and metal-exposed cercariae. However, with decreasing temperature a reduced rate of tail loss over time in metal-exposed cercariae compared to controls occurred at some low metal concentrations. When tail loss was compared against cercarial death of the experimental population toxic exposure induced changes in the parallel relationship of these parameters, dependent on individual metal concentration, water temperature and hardness. Differences in the relative effects of cadmium and zinc on cercariae were dependent on the environmental conditions of exposure. Both metals showed limited effects during the period of maximum cercarial infectivity (0-5 h). The mechanisms and importance of metal toxicity to cercarial tail loss are discussed.

Animals↗
PubMed2001

The relationship between tail biting in pigs, docking procedure and other management practices.

The tail length (docked, tipped or undocked) and tail status (bitten or unbitten) of 27,870 pigs from 450 units was recorded at six UK abattoirs. A farm survey of the final finishing stage was used to investigate the relationship between management practice and tail biting. This showed that docking was the most important factor influencing the probability of being not bitten, with 2.4% of docked and 8.5% of long-tailed pigs being tail-bitten. The following factors reduced the probability of long-tailed pigs being tail-bitten; light straw provision, use of natural ventilation or artificially controlled natural ventilation (ACNV), mixed sex grouping, meal or liquid feeding, and use of double or multi-space feeders. Docked and long-tailed pigs provided with light straw and natural ventilation/ACNV had levels of tail biting of 1.2% and 4.3% respectively; 3.9% of docked pigs with artificial ventilation and no straw were tail-bitten. Long-tailed pigs fed via double or multi-space feeders also had 3.9% of tails bitten.

Animal Husbandry↗
PubMed2000

Effects of tail amputation and treatment with an albendazole controlled-release capsule on the health and productivity of prime lambs.

OBJECTIVE: To assess the effects of tail amputation and treatment with albendazole controlled-release capsule (CRC) on the health and productivity of prime lambs. DESIGN: Field trials on three farms. ANIMALS: About 551 Coopworth-Poll Dorset cross, 588 Border Leicester-Merino-Poll Dorset cross and 575 Corriedale-Poll Dorset cross lambs. PROCEDURE: On three farms, lambs with amputated tails were compared with an equal number of lambs with tails left entire. In both of these groups half the lambs were treated with an albendazole CRC 13 weeks after the start of lambing. Faecal soiling of the breech and flystrike of the breech were recorded. Lambs were weighed and body condition scored at each visit and carcase weights and fat score of each lamb at slaughter. Procedures on the slaughter chain were monitored to determine whether the retention of the tail caused any problems. RESULTS: There were no observed benefits of treatment with an albendazole CRC on the farms in the study. There was no strong evidence that tail amputation had any long-term effect on the growth rate of lambs or carcase traits. No detrimental effects were observed during processing of lambs with long tails in the abattoir. Lambs with entire tails had significantly greater mean dag scores than lambs with amputated tails. On one farm lambs with entire tails were at about twice the risk of requiring crutching and on another farm were at three times the risk of breech strike compared with lambs with amputated tails. CONCLUSION: This study provides evidence that amputating the tail is not an absolute requirement to maintain the health and welfare of prime lambs, but leaving the tail of prime lambs entire is likely to increase chemical usage to control flystrike, and to increase the frequency of crutching.

Albendazole↗
PubMed2005

Structural characterization and assembly of the distal tail structure of the temperate lactococcal bacteriophage TP901-1.

The tail structures of bacteriophages infecting gram-positive bacteria are largely unexplored, although the phage tail mediates the initial interaction with the host cell. The temperate Lactococcus lactis phage TP901-1 of the Siphoviridae family has a long noncontractile tail with a distal baseplate. In the present study, we investigated the distal tail structures and tail assembly of phage TP901-1 by introducing nonsense mutations into the late transcribed genes dit (orf46), tal(TP901-1) (orf47), bppU (orf48), bppL (orf49), and orf50. Transmission electron microscopy examination of mutant and wild-type TP901-1 phages showed that the baseplate consisted of two different disks and that a central tail fiber is protruding below the baseplate. Evaluation of the mutant tail morphologies with protein profiles and Western blots revealed that the upper and lower baseplate disks consist of the proteins BppU and BppL, respectively. Likewise, Dit and Tal(TP901-1) were shown to be structural tail proteins essential for tail formation, and Tal(TP901-1) was furthermore identified as the tail fiber protein by immunogold labeling experiments. Determination of infection efficiencies of the mutant phages showed that the baseplate is fundamental for host infection and the lower disk protein, BppL, is suggested to interact with the host receptor. In contrast, ORF50 was found to be nonessential for tail assembly and host infection. A model for TP901-1 tail assembly, in which the function of eight specific proteins is considered, is presented.

Genes, Viral↗
PubMed1991

Mechanism of vasoconstriction in the rat's tail when warmed locally.

The vascular response of the tail to local warming was investigated in urethan-anesthetized rats whose colonic temperature was maintained at 39.5 degrees C with an intravenous thermode at an ambient temperature of 23 degrees C. The tail, covered with thin latex tubing, was immersed in temperature-controlled water initially kept at 35 degrees C. The tail was warmed by raising the water bath temperature from 35 to 44 degrees C at a constant rate. Tail blood flow (BF), mean arterial blood pressure (BP), and tail skin temperature (Tsk) were measured before and during the local warming. Tail vascular conductance (VC) was computed as 100 x tail BF/BP. When Tsk exceeded 37 degrees C, tail BF and VC significantly decreased from the levels at Tsk of 35 degrees C, and significant reductions in tail BF and VC occurred until Tsk reached 42 degrees C. Surgical deafferentation of the tail, chemical sympathectomy with 6-hydroxydopamine (100 mg/kg), and alpha-blockade with phentolamine (7 or 40.1-45.5 mg/kg) or phenoxybenzamine (5 mg/kg) failed to stop the decrease in tail BF and VC during the local warming. These results suggest that a reflex via the central nervous system and the alpha-adrenergic sympathetic nervous system is not indispensable for heat-induced vasoconstriction (HIVC). It is therefore assumed that, at least in the rat's tail, HIVC predominantly originates from a local vascular response to high temperature.

Animals↗
PubMed2006

Microgravity-induced modifications of the vestibuloocular reflex in Xenopus laevis tadpoles are related to development and the occurrence of tail lordosis.

UNLABELLED: During space flights, tadpoles of the clawed toad Xenopus laevis occasionally develop upward bended tails (tail lordosis). The tail lordosis disappears after re-entry to 1g within a couple of days. The mechanisms responsible for the induction of the tail lordosis are unknown; physical conditions such as weight de-loading or physiological factors such as decreased vestibular activity in microgravity might contribute. Microgravity (microg) also exerts significant effects on the roll-induced vestibuloocular reflex (rVOR). The rVOR was used to clarify whether tail lordosis is caused by physiological factors, by correlating the occurrence of microg-induced tail lordosis with the extent of microg-induced rVOR modifications. Post-flight recordings from three space flights (D-2 Spacelab mission, STS-55 in 1993; Shuttle-to-Mir mission SMM-06, STS-84 in 1997; French Soyuz taxi flight Andromède to ISS in 2001) were analyzed in these experiments. At onset of microgravity, tadpoles were at stages 25-28, 33-36 or 45. Parameters tested were rVOR gain (ratio between the angular eye movement and the lateral 30 degrees roll) and rVOR amplitude (maximal angular postural change of the eyes during a 360 degrees lateral roll). A ratio of 22-84% of tadpoles developed lordotic tails, depending on the space flight. The overall observation was that the rVOR of tadpoles with normal tails was either not affected by microgravity, or it was enhanced. In contrast, the rVOR of lordotic animals always revealed a depression. In particular, during post-flight days 1-11, tadpoles with lordotic tails from all three groups (25-28, 33-36 and 45) showed a lower rVOR gain and amplitude than the 1g-controls. The rVOR gain and amplitude of tadpoles from the groups 25-28 and 33-36 that developed normal tails was not affected by microgravity while the rVOR of microg-tadpoles from the stage-45 group with normal tails revealed a significant rVOR augmentation. IN CONCLUSION: (1) the vestibular system of tadpoles with lordotic tails is developmentally retarded by microgravity; (2) after a critical status of vestibular maturation obtained during the appearance of first swimming, microgravity activates an adaptation mechanism that causes a sensitization of the vestibular system.

Animals↗
PubMed2000

Function of the heterocercal tail in white sturgeon: flow visualization during steady swimming and vertical maneuvering.

Basal ray-finned fishes possess a heterocercal tail in which the dorsal lobe containing the extension of the vertebral column is longer than the ventral lobe. Clarifying the function of the heterocercal tail has proved elusive because of the difficulty of measuring the direction of force produced relative to body position in the aquatic medium. We measured the direction of force produced by the heterocercal tail of the white sturgeon (Acipenser transmontanus) by visualizing flow in the wake of the tail using digital particle image velocimetry (DPIV) while simultaneously recording body position and motion using high-speed video. To quantify tail function, we measured the vertical body velocity, the body angle and the path angle of the body from video recordings and the vortex ring axis angle and vortex jet angle from DPIV recordings of the wake downstream from the tail. These variables were measured for sturgeon exhibiting three swimming behaviors at 1.2 L s(-)(1), where L is total body length: rising through the water column, holding vertical position, and sinking through the water column. For vertical body velocity, body angle and path angle values, all behaviors were significantly different from one another. For vortex ring axis angle and vortex jet angle, rising and holding behavior were not significantly different from each other, but both were significantly different from sinking behavior. During steady horizontal swimming, the sturgeon tail generates a lift force relative to the path of motion but no rotational moment because the reaction force passes through the center of mass. For a rising sturgeon, the tail does not produce a lift force but causes the tail to rotate ventrally in relation to the head since the reaction force passes ventral to the center of mass. While sinking, the direction of the fluid jet produced by the tail relative to the path of motion causes a lift force to be created and causes the tail to rotate dorsally in relation to the head since the reaction force passes dorsal to the center of mass. These data provide evidence that sturgeon can actively control the direction of force produced by their tail while maneuvering through the water column because the relationship between vortex jet angle and body angle is not constant.

Animals↗
PubMed2001

The dynamics and scaling of force production during the tail-flip escape response of the California spiny lobster Panulirus interruptus.

The tail-flip escape behavior is a stereotypical motor pattern of decapod crustaceans in which swift adduction of the tail to the thorax causes the animal to rotate, move vertically into the water column and accelerate rapidly backwards. Previous predictions that a strong jet force is produced during the flip as the tail adducts to the body are not supported by our simultaneous measurements of force production (using a transducer) and the kinematics (using high-speed video) of tail-flipping by the California spiny lobster Panulirus interruptus. Maximum force production occurred when the tail was positioned approximately normal to the body. Resultant force values dropped to approximately 15% of maximum during the last third of the flip and continued to decline as the tail closed against the body. In addition, maximum acceleration of the body of free-swimming animals occurs when the tail is positioned approximately normal to the body, and acceleration declines steadily to negative values as the tail continues to close. Thus, the tail appears to act largely as a paddle. Full flexion of the tail to the body probably increases the gliding distance by reducing drag and possibly by enhancing fluid circulation around the body. Morphological measurements indicate that Panulirus interruptus grows isometrically. However, measurements of tail-flip force production for individuals with a body mass (Mb) ranging from 69 to 412 g indicate that translational force scales as Mb0.83. This result suggests that force production scales at a rate greater than that predicted by the isometric scaling of muscle cross-sectional area (Mb2/3), which supports previously published data showing that the maximum accelerations of the tail and body of free-swimming animals are size-independent. Torque (tau) scaled as Mb1.29, which is similar to the hypothesized scaling relationship of Mb4/3. Given that tau is proportional to Mb1.29, one would predict rotational acceleration of the body (alpha) to decrease with increasing size as Mb(-0.37), which agrees with previously published kinematic data showing a decrease in alpha with increased Mb.

Analysis of Variance↗
PubMed2001

Natural attenuation potential of cyanide via microbial activity in mine tailings.

Biological removal by indigenous microflora of cyanide, contained in old (6-9 years) and fresh tailings (3 months), was studied in order to assess its natural attenuation potential via biodegradation. To investigate the presence of indigenous microflora in tailings, total heterotrophic and cyanide resistant bacteria were counted using the spread-plate method. The free cyanide mineralization potential was estimated using K14CN in the presence of various unlabeled cyanide concentrations (0, 5, and 10 mg CN/kg). The biodegradation of cyanide contained initially in the samples was also investigated by monitoring formate, formamide, ammonia and total cyanide (CNT) concentrations over 111 days. The enumeration of total heterotrophic and cyanide-resistant bacteria in old tailings showed an average population of 105 cfu/g. However, no growth was detected in fresh tailings. Nevertheless, cyanide mineralization tests indicated the presence, in both old and fresh tailings, of a cyanide-degrading microflora. In old tailings, maximum mineralization percentages of free cyanide ranging from 85% to 100% were obtained after 65 days at all concentrations tested. A mineralization percentage of 83% after 170 days was also observed in fresh tailings. No decrease of total cyanide concentration in old tailings was observed when the biodegradation of endogenous cyanide was tested whereas a significant decrease was recorded in fresh tailings after 96 days. The presence of strong metal-cyanide complexes resistant to biodegradation could explain the absence of biodegradation in old tailings. This study demonstrated the presence of an indigenous free cyanide-degrading microflora in both old and fresh tailings, and suggests that natural attenuation of cyanide in gold mine tailings is likely to occur via microbial activity.

Bacteria↗
PubMed1992

Acceleration of tail pinch-induced feeding in rats by analgesic effect of neurotropin.

Mechanisms of tail pinch-induced feeding and effects of neurotropin (NSP), an extract from the inflamed skin of rabbit inoculated with vaccinia virus, on behavioral responses were investigated in rats. Treatment of a 5-min tail pinch (tail pinch I) induced feeding response. An intensified 15-min tail pinch (tail pinch II) provoked emotional reactions besides feeding behavior. The rate of food intake (food intake/tail pinch duration) during tail pinch II was less than that at tail pinch I. Intraperitoneal administration of NSP (100 mg/kg/day) by itself produced no remarkable change in feeding or emotional behavior. However, NSP-treated rats increased eating size and prolonged eating duration during tail pinch I. Pretreatment of NSP increased feeding behavior more potently at tail pinch II than at tail pinch I and decreased the incidence of emotional reactions at tail pinch II. The results suggest that NSP, by its analgesic action, may modulate behavioral responses during tail pinch treatment through selective blockade of the nociceptive and feeding-inhibitory information, but not through the nonnociceptive and feeding-excitatory signals.

Analgesics↗
PubMed2004

Anaerobic biodegradation of an organic by-products leachate by interaction with different mine tailings.

Deinking by-products from paper recycling have been used as cover materials on acid-producing tailings. Due to residual cellulose, anaerobic degradation leads to the production of an organic-rich leachate, which may percolate through the tailings. This study aims at describing the influence of the tailings' characteristics on the attenuation of organic matter in leachate and at discussing the degradation mechanisms. To this end, leachate was mixed with different types of tailings, including three unoxidized tailings with varying acid generation potentials and one tailing in three states of oxidation. Regularly, selected biochemical parameters were analyzed to access the evolution of organic components. The results show that when leachate from deinking by-products was placed in contact with tailings, phase and acid-base balance reactions took place in the beginning. Subsequently, oxidation-reduction reactions dominated the chemistry of the system. The type, the constituents, and the state of oxidation of the mine tailings condition the mechanisms of biodegradation of organic components. Methanogenesis was predominant in the control sample (pure organic leachate) but was absent in all leachate-tailings mixtures. No biodegradation was observed in the liquid phase for oxidized tailings and the organic concentration remained constant for unoxidized tailings, independently of the acid-generation potential. The biodegradation efficiency was optimal when the leachate was in contact with a mixture of oxidized and unoxidized tailings due to sulfate-reduction.

Acids↗
PubMed2004

Influence of Typha latifolia and fertilization on metal mobility in two different Pb-Zn mine tailings types.

Storing metal-rich mine waste (tailings) under submerged and reduced conditions can prevent the release of metals to the water column, but introduction of wetland plants on these sediments may alter the reducing environment through root oxygen diffusion or organic matter accumulation. Fertilization of these wetlands can enhance plant growth, but also may either strengthen reducing conditions via microbial stimulation, or increase the redox potential (Eh) through increased root radial oxygen loss. This long-term study (2.25 years) investigated the porewater As, Fe, and Zn concentrations of waterlogged Pb-Zn tailings from two Irish mines, Silvermines and Tara mines, with addition of Typha latifolia, fertilizer, or both treatments combined. In both tailings types, the fertilized plants showed significantly increased total biomass production, but the plants grew greater biomass in Tara tailings relative to Silvermines tailings even without fertilization. In Tara mines tailings, the addition of plants increased Eh and mobilized Zn; the addition of fertilizer enhanced reducing conditions and increased porewater concentrations of As and soluble sulfides; and the combination of treatments on these tailings resulted in complex interactions. In Silvermines tailings, there were negligible effects of the treatments. For effective sequestration of metals in these tailings, Silvermines would require only water cover, but Tara mines tailings would require either both treatments or neither because each treatment individually would increase solubility of As or Zn. These results show also the necessity of evaluating treatment effects specific to individual tailings, that long-term studies (years) are crucial for tailings equilibration and valid experimental conclusions, and that passive accumulation of organic matter may take decades.

Biodegradation, Environmental↗
PubMed2000

Acute castration and/or tailing distress and its alleviation in lambs.

PURPOSES AND APPROACH: Acute castration and/or tailing distress in lambs has been examined extensively during the last decade. At least 59 different approaches to assessing and alleviating this distress have been reported so that the literature is quite complex. The purpose of this paper is to provide an overview of the literature on castration and/or tailing distress, where the distress was assessed using acute changes in plasma cortisol concentrations. A method of analysis involving the integrated cortisol response (i.e. the areas under the cortisol curves while the plasma concentration is above pretreatment values) to each treatment and using treatments which were common to different studies as reference points, allowed meaningful comparison within and between studies. A 6-point ranking scale emerged, where rank 1 represented the least distress and rank 6 the most distress. COMPARISON OF ACUTE DISTRESS RESPONSES: This analysis revealed the following major points. Surgical methods of castration and/or tailing cause the greatest cortisol responses (rank 5 or 6). Most ring and ring plus clamp methods of castration plus tailing or castration, used without a local anaesthetic or systemic analgesic, cause rank 4 responses. One form of ring plus clamp castration (i.e. applying the clamp for 10 s across the full width of the scrotum distal to the ring in lambs aged no more than 1 week) reduces the cortisol response to rank 1. When these lambs are also tailed by applying a ring and clamp in a similar manner to the tail, they also exhibit a rank 1 response. Local anaesthetic given 10-20 or 12 min or 10-15 s before or immediately after ring only castration and/or tailing can virtually abolish the cortisol response (rank 1), depending on the site(s) of injection. For ring or ring plus clamp castration, the most effective sites (as judged by cortisol responses) are the neck of the scrotum or the testes. Delivery of local anaesthetic to achieve successful nerve blockade can be by needle, high-pressure needleless administration or, for the tail only, by an aerosol spray. Local anaesthetic injected into the scrotal neck, spermatic cords and/or testes has little effect on the overall cortisol response to clamp castration. Reductions in cortisol responses to clamp castration or to ring tailing can occur after administration of non-steroidal anti-inflammatory drugs. Most tailing methods elicit cortisol responses that are several ranks lower than those caused by castration plus tailing or castration alone. Although tailing by most methods elicits rank 1 cortisol responses, the use of local anaesthetic or non-steroidal anti-inflammatory drugs can reduce the response within the rank 1 range. RECOMMENDATION: Farmers should be encouraged to choose the lowest ranked method that is economically and practically feasible for them. Specific methods such as surgical castration should be discouraged.

Journal Article↗
PubMed1993

Acceleration of bovine neurofilament L assembly by deprivation of acidic tail domain.

Functions of the tail region of neurofilament L have, to date, not been clearly elucidated. Bovine neurofilament L was cleaved into tail-less neurofilament L (50 kDa) and a tail fragment (19 kDa), by thrombin. Tail-less neurofilament L was deficit of the highly acidic domain of the tail region (approximately 77% of the entire region). Assembly of tail-less neurofilament L. was observed to be accelerated by both fluorometric and centrifugal measurements, compared with intact neurofilament L. The critical concentration of tail-less neurofilament L, which constitutes the constant unassembled pool, was approximately 0.25-times lower than that of neurofilament L. Under physiological conditions, tail-less neurofilament L formed a ribbon-like structure, whereas tail-less neurofilament L could form 10-nm filaments in an extremely low ionic-strength buffer in the presence of 1 mM MgCl2. An affinity-purified antibody directed against the tail fragment also accelerated neurofilament L assembly. The tail fragment neither coassembled with neurofilament L nor affect neurofilament L assembly. The acidic domain of the tail region may regulate neurofilament assembly and may be involved in 10-nm filament formation under physiological conditions.

Amino Acid Sequence↗
PubMed1995

Na-Ca exchange tail current indicates voltage dependence of the Cai transient in rabbit ventricular myocytes.

INTRODUCTION: In mammalian cardiac myocytes, a rise of intracellular calcium (Cai) is well known to activate Ca extrusion via forward Na-Ca exchange, which generates an inward membrane current. This can be observed as an inward "tail" current (INa-Ca) when the membrane is repolarized after a depolarization-activated rise of Cai. If, during a voltage step, the membrane is repolarized at the time of the peak of the Cai transient, the size of the INa-Ca tail might be expected to reflect the magnitude of the Cai transient. Therefore, it might be possible to estimate the amplitude and voltage dependence of the Cai transient without, for instance, using fluorescent indicators that can interfere with Cai regulation. The first aim of this study was to use INa-Ca tails to investigate the voltage dependence of the Cai transient in whole cell patch clamped rabbit ventricular myocytes dialyzed with a "normal" level of internal Na. The second aim was to investigate how the voltage dependence of the INa-Ca tails varied with changes to the dialyzing Na concentration. The third aim was to test the correlation of voltage dependence of INa-Ca tails with the voltage dependence of the Cai transient obtained using a fluorescent Ca indicator. METHODS AND RESULTS: Experiments were performed at 35 degrees to 37 degrees C using whole cell patch clamp, and the holding potential was set at -40 mV. Depolarization elicited a Cai transient that peaked in 40 to 50 msec. We reasoned, therefore, that membrane repolarization after 50 msec would cause the raised level of Cai to activate an inward current on forward Na-Ca exchange. The amplitude of INa-Ca measured shortly (10 msec) after repolarization should reflect the peak amplitude of the Cai transient elicited by the depolarization. In cells dialyzed with 10 mM Na-containing solution and depolarized for 50 msec to differing test potentials, the INa-Ca tail on repolarization increased progressively after pulses to between -40 and +20 mV. The INa-Ca tail was maximal after a +20-mV pulse and showed no decline after depolarizations to more positive potentials, up to +100 mV (P > 0.1; n = 8). This implies that the Cai transient has a similar amplitude for depolarizing pulses between +20 and +100 mV. When Na-free solution dialyzed the cell, the voltage dependence of the INa-Ca tail became bell-shaped, with a maximum at +20 mV (n = 4). Voltage dependence of the INa-Ca tail was little affected by raising dialyzing Na from 10 to 20 mM (n = 4); but the amplitude of the INa-Ca tail increased. Inhibition of the Na-K pump with strophanthidin in cells dialyzed with 10 mM Na had qualitatively similar effects to increasing dialyzing Na. In Fura-2 loaded cells dialyzed with 10 mM Na, the Cai transient exhibited a similar voltage dependence to the INa-Ca tail (n = 6). CONCLUSION: The results of this study suggest that in cells dialyzed with 10 mM Na, the voltage dependence of the Cai transient is different from the L-type Ca current, since this current declines at potentials > +20 mV. The results obtained using Fura-2 suggest that the INa-Ca tail current measurement tracked the Cai sufficiently well to reflect the voltage dependence of the Cai transient. The data also confirm that the voltage dependence of the Cai transient in rabbit cells can be modulated by altering dialyzing Na concentration.

Animals↗
PubMed2000

Occurrence of sulfate-reducing bacteria under a wide range of physico-chemical conditions in Au and Cu-Zn mine tailings.

Sulfate-reducing bacteria (SRB) have been observed in mining environments, but their presence has not been linked to specific physico-chemical and mineralogical factors. The present study was undertaken to assess the presence of SRB in several Au and Cu-Zn mine tailings located near Timmins, Ont., Canada, and determine the factors responsible for their presence. Vegetated and non-vegetated mine tailings were sampled for SRB enumeration, pH, Eh, water content, total carbon content and sequential chemical extraction. Results first showed that SRB populations were present at all sites and that their distribution varied with depth. Populations were recovered from neutral pH and slightly anoxic tailings and from highly acidic (pH 2) and oxic tailings. The total carbon content of the tailings was generally low and not related to the presence of vegetation. In addition, the carbon content did not affect SRB population distribution and appeared to be more related to the type of tailings, i.e., oxidized and acidic Cu-Zn tailings contained on average more carbon than Au tailings. Results also indicated that the water content of the tailings varied greatly with depth and was not related to the presence of SRB populations. The sequential chemical extraction showed that the pyrite content of the tailings was lower in Au tailings than in Cu-Zn tailings, and that some oxidized Cu-Zn sites were depleted in pyrite due to microbial and chemical oxidation. Our results indicate that SRB could be cultured from a variety of sites and sample types, and that factors such as pH, Eh, water content and carbon content at the collection sites did not exert control on their presence.

Journal Article↗
PubMed2006

Utilization of gold tailings as an additive in Portland cement.

Mine tailings are formed as an industrial waste during coal and ore mining and processing. In the investigated process, following the extraction of gold from the ore, the remaining tailings are subjected to a two-stage chemical treatment in order to destroy the free cyanide and to stabilize and coagulate heavy metals prior to discharge into the tailings pond. The aim of this study was the investigation of the feasibility of utilization of the tailings as an additive material in Portland cement production. For this purpose, the effects of the tailings on the compressive strength properties of the ordinary Portland cement were investigated. Chemical and physical properties, mineralogical composition, particle size distribution and microstructure of the tailings were determined by Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), particle size analyzer (Mastersizer) and scanning electron microscope (SEM). Following the characterization of the tailings, cement mortars were prepared by intergrinding Portland cement with dried tailings. Composition of the cement clinkers were adjusted to contain 5, 15, 25% (wt/wt) dried tailings and also silica fume and fly ash samples (C and F type) were added to clinker in different ratios. The mortars produced with different amounts of tailings, silica fume, fly ashes and also mixtures of them were tested for compressive strength values after 2, 7, 28 and 56 days according to the European Standard (EN 196-1). The results indicated that gold tailings up to 25% in clinker could be beneficially used as an additive in Portland cement production. It is suggested that the gold tailings used in the cement are blended with silica fume and C-type fly ash to obtain higher compressive strength values.

Gold↗