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At least 541 records · Page 30Linked to original sources

Hedgehog signaling controls dorsoventral patterning, blastema cell proliferation and cartilage induction during axolotl tail regeneration.

Tail regeneration in urodeles requires the coordinated growth and patterning of the regenerating tissues types, including the spinal cord, cartilage and muscle. The dorsoventral (DV) orientation of the spinal cord at the amputation plane determines the DV patterning of the regenerating spinal cord as well as the patterning of surrounding tissues such as cartilage. We investigated this phenomenon on a molecular level. Both the mature and regenerating axolotl spinal cord express molecular markers of DV progenitor cell domains found during embryonic neural tube development, including Pax6, Pax7 and Msx1. Furthermore, the expression of Sonic hedgehog (Shh) is localized to the ventral floor plate domain in both mature and regenerating spinal cord. Patched1 receptor expression indicated that hedgehog signaling occurs not only within the spinal cord but is also transmitted to the surrounding blastema. Cyclopamine treatment revealed that hedgehog signaling is not only required for DV patterning of the regenerating spinal cord but also had profound effects on the regeneration of surrounding, mesodermal tissues. Proliferation of tail blastema cells was severely impaired, resulting in an overall cessation of tail regeneration, and blastema cells no longer expressed the early cartilage marker Sox9. Spinal cord removal experiments revealed that hedgehog signaling, while required for blastema growth is not sufficient for tail regeneration in the absence of the spinal cord. By contrast to the cyclopamine effect on tail regeneration, cyclopamine-treated regenerating limbs achieve a normal length and contain cartilage. This study represents the first molecular localization of DV patterning information in mature tissue that controls regeneration. Interestingly, although tail regeneration does not occur through the formation of somites, the Shh-dependent pathways that control embryonic somite patterning and proliferation may be utilized within the blastema, albeit with a different topography to mediate growth and patterning of tail tissues during regeneration.

Ambystoma↗

TLP-1 is an asymmetric cell fate determinant that responds to Wnt signals and controls male tail tip morphogenesis in C. elegans.

We have isolated mutations defining a new gene, tlp-1, that affect asymmetric cell fates and morphogenesis during the development of the C. elegans tail. tlp-1 mutations cause defects in the specification of asymmetric cell fates in the descendants of the T blast cell, whose polarity is controlled by Wnt signaling and cause abnormal male tail development leading to the formation of a posterior protrusion reminiscent of 'leptoderan', or pointy tailed, nematode species. In wild-type C. elegans males, which have a 'peloderan' or rounded tail, retraction of the tail tip hypodermis involves a temporally ordered set of cell fusions and changes in cell shape that appear to be heterochronically delayed in tlp-1 males, suggesting that subtle changes in these events can bring about evolutionary changes in morphology. tlp-1 encodes a C2H2 zinc-finger protein that is a member of the Sp family of transcription factors. A TLP-1::GFP fusion protein is expressed in the nuclei of many cells during early embryogenesis and then becomes restricted primarily to posterior cells. At hatching, it is expressed in several head neurons, the posterior intestine cells, tail hypodermal cells, the T cells and specific T-cell descendents in a pattern that suggests TLP-1 may be asymmetrically expressed during the divisions of the T cell lineage. Furthermore, the asymmetry of TLP-1 expression and function appears to be controlled by Wnt signals that control T cell polarity. These results suggest that tlp-1 encodes a transcription factor required for cellular asymmetry that functions downstream of Wnt signals that control cell polarity, as well as in cell fusion and patterning in the C. elegans tail.

Animals↗

The tale of the tail: limb function and locomotor mechanics in Alligator mississippiensis.

Crocodilians tow their large muscular tail behind them during terrestrial bouts when they high walk (a walking trot). Analysis of ground reaction forces in the American alligator (Alligator mississippiensis) revealed the consequences of tail-dragging. Individual limb and tail ground reaction force records show that the hindlimbs of Alligator take on a substantial role in body mass support consistent with the more caudal location of its center of mass due to the presence of a particularly heavy tail (representing nearly 28% of total body mass). Furthermore, because the constant drag imposed by the tail is substantial, both fore- and hindlimbs in Alligator have a heightened propulsive role as a means of countering the net braking effect of the tail. Ground reaction forces of the whole body were used to assess how well Alligator was able to utilize mechanical energy-saving mechanisms (inverse pendulum or mass-spring). A high-walking Alligator recovers, on average, about 20% of its mechanical energy by inverse pendulum mechanics. These modest energy recovery levels are likely to be due to a combination of factors that may include low locomotor speed, imprecise coordination of contralateral limbs in the trot, frequent dragging of feet of protracting limbs during swing phase and, possibly, tail dragging.

Alligators and Crocodiles↗

Evaluation of blood pressure measured by tail-cuff methods (without heating) in spontaneously hypertensive rats.

Conventional noninvasive blood pressure in conscious rats or mice are typically measured using the tail-cuff method after heating the animal. The goal of this study was to assess the validity of a novel tail-cuff method without animal heating when compared with the conventional heating tail-cuff method (unanesthetized rats with heating), telemetry method (unanesthetized restrained rats without heating), or carotid arterial catheter method (anesthetized rats, carotid arterial cannulation). The blood pressure and heart rate of spontaneously hypertensive rats were measured at 13:00-17:00 h for all experiments. Experiments demonstrated similar systolic blood pressure measurements when comparing the unheated-animal tail-cuff method and the telemetry method. Further, values obtained by both methods were lower than those obtained by the heated-animal tail-cuff method. Systolic blood pressure measurements obtained through carotid arterial cannulation were lower than those obtained by any other method. The heart rate was highest using the unheated-animal tail-cuff method when compared with the other methods. These data suggest that the novel unheated-animal tail-cuff method is a sensitive and accurate approach for the noninvasive measurement of blood pressure in conscious rats.

Animals↗

Corticosterone, adrenal and spleen weight in mice after tail bleeding, and its effect on nearby animals.

Experiments were performed in mice to study if stress was involved in tail bleeding and to investigate any transmittable signal at killing. A second study looked at the time taken to recover from stress elicited by these procedures. Corticosterone levels were significantly higher in mice immediately after the completion of tail bleeding than in control mice (P < 0.05) suggesting that tail bleeding in mice was stressful. This study did not show any evidence for an odour or sound being released during killing or tail bleeding as there was no significant effect on corticosterone levels in mice present in the same room at the time these procedures were carried out. Corticosterone levels in mice killed on days 1, 3, and 7 after tail bleeding were significantly lower (P < 0.05) than the average corticosterone level in tail blood on day 1, indicating that mice recovered within 24 h from the stress of tail bleeding.

Adrenal Glands↗

Tail-swing behavior: a novel animal model for anxiety.

The present study was designed to examine the effects of diazepam, nitrazepam, desipramine and haloperidol on tail-swing behavior in mice and to characterize the effects of diazepam. Mice were suspended with rubber bands tied around their upper bodies in order to force their heads upwards. The duration of tail-swing behavior was then measured. Diazepam (0.3 and 1 mg/kg) and nitrazepam (0.3 and 1 mg/kg) significantly depressed tail-swing behavior, while they did not affect ambulation or muscle tone. In contrast, desipramine (10-30 mg/kg) did not affect tail-swing behavior, but at doses of 17.5 and 30 mg/kg produced a marked reduction in ambulation. Haloperidol (0.15 mg/kg) significantly decreased both tail-swing behavior and ambulation. The benzodiazepine receptor antagonist flumazenil (1 and 10 mg/kg), the benzodiazepine receptor inverse agonist beta-carboline-3-carboxylic acid N-methylamide (beta-CCM; 3 mg/kg) and the GABA(A) receptor antagonist bicuculline (3 mg/kg) reversed the effects of diazepam (1 mg/kg) on tail-swing behavior, although administered alone they failed to influence such behavior. These results suggest that anxiety and/or fear are responsible for tail-swing behavior.

Animals↗

Effects of tail docking using a rubber ring with or without anesthetic on behavior and production of lactating cows.

Production and behavioral measures were recorded to determine the level of stress and pain associated with tail docking adult dairy cows with a rubber ring. The possible advantages of using an epidural anesthetic were also examined. Sixty-four lactating, mixed-parity, Holstein cows were randomly assigned to one of four treatment groups. The treatments were rubber ring docking with epidural anesthetic (RRA), rubber ring docking without anesthetic (RR), control with epidural anesthetic (CA), and control without anesthetic (C). Behavior was examined on d 0, +1, +2, and +6. Milk production and feed intake were monitored. Cows exhibited subtle behavioral changes following application of rubber rings, as well as after epidural administration on d 0 and tail amputation on d +6. After treatment on d 0, the RR, RRA, and CA groups displayed less tail shaking than the C group. The RR and RRA cows continued to exhibit less tail shaking on d +1, +2, and +6. Also on d 0, the RR and RRA groups held their tails in the raised position less than the C and CA groups. After amputation on d +6, the RR and RRA groups spent longer with their tails pressed to their bodies than the C and CA groups. No significant differences in milk production or feed intake were found. Results suggest that tail-docking adult dairy cattle with rubber rings causes, at most, mild discomfort and that there is no benefit in using an epidural anesthetic. However, long-term effects need to be investigated.

Amputation, Surgical↗

Responses to tail docking in calves and heifers.

The primary objective of this study was to determine the behavioral and physiological effects of tail banding and atrophy using rubber rings 2 to 4 mo before first parturition in dairy heifers either with or without the use of epidural anesthesia. The secondary objective was to determine behavioral responses to tail banding using rubber rings in calves 7 to 42 d of age. Preparturient heifers (n = 24) were randomly assigned to one of four treatment groups: 1) tails were cleaned and handled; 2) tails were cleaned, handled, and an elastrator band was applied to the tail; 3) an epidural was administered 15 min before cleaning and handling; and 4) an epidural was administered 15 min before application of an elastrator band. Behavioral observations and physiological responses were collected for 6 wk. Additionally, behavioral responses to tail banding were recorded for 10 d on Holstein heifer calves that were 1 to 6 wk of age (n = 40). No significant differences in behavior were observed among treatment groups of preparturient heifers at any time during the 6-wk observation period. Preweaned calves that were 21 to 42 d of age demonstrated significantly more restlessness after application of tail bands compared to younger calves or control calves of the same age. Plasma cortisol values of preparturient heifers remained within limits previously described for nonstressed animals and no significant differences were detected among groups. Hematological values remained within the reference values for cattle, and there were no significant differences between groups except for relatively more eosinophils in the heifers that received epidurals. No significant differences in heart rate or body temperature were detected among groups.

Amputation, Surgical↗

Increased tail artery vascular responsiveness to angiotensin II in cold-treated rats.

Chronic exposure of rats to cold for 1-3 weeks results in a mild form of hypertension. The renin-angiotensin system (RAS) has been implicated in this model of cold-induced hypertension. Previously we have characterized the vascular responsiveness in cold-acclimated animals, using aortic tissue, and recent studies have focused on the thermoregulatory responses of angiotensin II (AngII), utilizing the tail artery of the rat. Therefore in the current study we evaluated the vascular responsiveness of cold-treated rats to AngII in both aorta and tail artery at 2 and 4 weeks of cold exposure (5+/-2 degrees C). Systolic blood pressures were significantly elevated in cold-treated animals compared with control animals at both 2 and 4 weeks of cold exposure. At both of these time points body weights were reduced and ventricular weights were increased in cold-treated animals. After 2 weeks of cold exposure the vascular responsiveness of the aorta to AngII was significantly lower than that of controls. This vascular responsiveness to AngII was elevated and returned to control levels after 5 weeks of cold exposure. However, this pattern was not observed in the tail artery. The vascular responsiveness of tail artery rings from cold-treated rats to AngII was significantly greater than that of control animals during both 2 and 5 weeks of exposure to cold. The vascular contractile responses of both the aorta and tail artery to KCI in the cold-treated animals was not different from that of the control animals maintained at ambient room temperature, suggesting that the vascular smooth muscle contractile components were not altered by the cold exposure. Thus, the in vitro vascular reactivity to the receptor-mediated vasoconstrictor AngII was decreased in the sparsely innervated aorta and increased in the more densely innervated tail artery of the cold-treated animals when compared with controls. These results suggest that the increased responsiveness of AngII on the smooth muscle of the tail artery may play a role in adaptation to the cold and the maintenance of cold-induced hypertension.

Angiotensin II↗

Serotonin release evoked by tail nerve stimulation in the CNS of aplysia: characterization and relationship to heterosynaptic plasticity.

Considerable experimental evidence suggests that serotonin (5-HT) at sensory neuron-->motor neuron (SN-->MN) synapses, as well as other neuronal sites, contributes importantly to simple forms of learning such as sensitization and classical conditioning in Aplysia. However, the actual release of 5-HT in the CNS induced by sensitizing stimuli such as tail shock has not been directly demonstrated. In this study, we addressed this question by (1) immunohistochemically labeling central 5-HT processes and (2) directly measuring with chronoamperometry the release of 5-HT induced by pedal tail nerve (P9) shock onto tail SNs in the pleural ganglion and their synapses onto tail MNs in the pedal ganglion. We found that numerous 5-HT-immunoreactive fibers surround both the SN cell bodies in the pleural ganglion and SN axons in the pedal ganglion. Chronoamperometric detection of 5-HT performed with carbon fiber electrodes implanted in the vicinity of tail SN somata and synapses revealed an electrochemical 5-HT signal lasting approximately 40 sec after a brief shock of P9. 5-HT release was restricted to discrete subregions (modulatory fields) of the CNS, including the vicinity of tail SN soma and synapses ipsilateral to the stimulation. Increasing P9 shock frequency augmented the amplitude of the 5-HT signal and, in parallel, increased SN excitability and SN synaptic transmission onto tail MNs. However, the relationship between the amount of 5-HT release and the two forms of SN plasticity was not uniform: SN excitability increased in a graded manner with increased 5-HT release, whereas synaptic facilitation exhibited a highly nonlinear relationship. The development of chronoamperometric techniques in Aplysia now paves the way for a more complete understanding of the contribution of the serotonergic modulatory pathway to memory processing in this system.

Action Potentials↗

Method to quantify tail vein injection technique in small animals.

Injection errors, which are often not readily recognized, can greatly impact the outcome of a pre-clinical research study. As a result, unrecognized misadministration of test compounds can render a high cost to the biomedical community. In this report, we propose six criteria for a reagent designed to assess tail vein injection technique in small animals and suggest a reagent, colloidal gold labeled with the stable isotope 197Au, that satisfies these criteria, thereby describing and validating for the first time a method to quantify technical compliance in tail vein injections. In an application of this reagent, we show the degree of variation experienced by technologists performing tail vein injection procedures in mice. In this study, mice were manually restrained and received an injection in the tail vein. One hour after injection, the mice were euthanized, various organs including the tail (the site of the injection) were collected, and their gold content was quantified by neutron activation. The three experienced animal technologists in the study were tested for tail vein injection proficiency in 30 mice. Prior to the study, the supervisor stated that a misinjection occurs when more than 10% of the intended volume remains in the tail. In light of this criterion, 12 of the 30 injections were misadministered: two with technologist 1, three with technologist 2, and seven with technologist 3. Although she was able to correctly rank the injection skills of the three technologists used in this experiment, i.e., technologist 1 and 2 more better skilled than technologist 3, the supervisor greatly underestimated the extent and degree of injection failures for the procedure. The results of the study illustrate the potential problems associated with the technical compliance with this common laboratory procedure and suggest that there is a need to validate injection methods and a need to monitor technical competence. Application of reagents similar to colloidal gold and the methods presented will facilitate the development of improved methods of teaching injection technique and monitoring technical quality in the laboratory setting. In Vivo Micro Computed Tomography of Subchondral Bone in the Rat After Intra-articular Administration of Monosodium Iodoacetate

Animals↗

[Ameliorative effect of ginseng glycopeptide on cross-linking of rat tail tendon collagen].

OBJECTIVE: To investigate the ameliorative effect of ginseng glycopeptide on cross-linking of rat tail tendon collagen. METHOD: ELISA was used to determine the inhibitory effect of ginseng glycopeptide on cross-linking of rat tail tendon collagen in vitro. After ginseng glycopeptide was intraperitoneally administrated to streptozotocin-induced diabetic rats for 12 weeks, the acid solubility, limited pepsin degradation properties and solubility in SDS-2-mercaptoethanol of the rat tail tendon collagen were determined, and the effect of ginseng glycopeptide on the tail tendon collagen cross-linking was evaluated. RESULT: Ginseng glycopeptide inhibited significantly the cross-linking of rat tail tendon collagen in vitro. The solubility of the tail tendon collagen (in acid, pepsin and SDS-2-mercaptoethanol) was markedly decreased in diabetic rats and ginseng glycopeptide-treated diabetic rats had significantly an increase in the collagen solubility in the above-mentioned solutions, suggesting that ginseng glycopeptide decreased severity of the collagen cross-linking. CONCLUSION: Ginsengglycopeptide exhibits an significantly ameliorative effect on cross-linking of rat tail tendon collagen.

Animals↗

A low cost tail-cuff method for the estimation of mean arterial pressure in conscious rats.

Methods utilized in the determination of systolic tail-cuff pressure (TCP) in awake rats are aimed at detecting the earliest possible tail pulsations as the cuff is deflated. In the method described in this study, a small, inexpensive electret microphone is used as a sensor, connected to the tail by a piece of rubber tubing. This design provides selective attenuation of tail pulsations appearing as the cuff is deflated between systolic and mean arterial pressures. In this manner, tail pulsations are detected only when the cuff pressure is lowered below the mean arterial pressure, thus providing an estimation of the latter. The method was validated in prewarmed awake normotensive and hypertensive rats by simultaneous comparison with directly measured systolic and mean pressures or with a conventional tail-cuff method. Validation studies were also carried out in anesthetized rats undergoing wide variations of arterial pressure by parenteral injections of norepinephrine or nitroprusside. Close agreement was observed between TCP determined with this method and directly obtained mean, but not systolic, pressure. Thus, the method described in this study constitutes an inexpensive alternative to conventional tail-cuff methods. Mean, rather than systolic pressure, appears to be evaluated in the conscious rat by employing this method.

Animals↗

Non-invasive blood pressure measurement in Yucatan miniature swine using tail cuff sphygmomanometry.

A relatively new non-invasive method using a photo-electric flow sensor in non-heated animals, was evaluated for its accuracy in measuring systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial pressure (MAP) in 40-90 Kg normotensive and hypertensive Yucatan miniature swine. Directly measured SBP, DBP and electronically averaged MAP were recorded from chronic arterial catheters simultaneously with indirect pressures, cuff pressure and tail blood flow under various conditions. In all of the tests tail cuff SBP estimation averaged within 5% of directly measured SBP. The correlation of the two methods was significant (r = .95, P less than 0.01). Over a 60 to 202 mmHg range of blood pressure induced pharmacologically or due to DOCA hypertension, the tail cuff SBP was within 4-10% of directly measured SBP. The tail cuff method was also used to determine DBP and MAP. DBP determined from the tail cuff record was found consistently to underestimate the direct measured DBP by approximately 17%. The two methods were correlated (r = .87 P less than 0.01). The measured tail cuff MAP generally underestimated the direct MAP by approximately 5%. The correlation of directly measured MAP and tail cuff methods was significant (r = .72, P less than 0.01). These results indicated that this system may be used to accurately assess blood pressure in miniature swine.

Animals↗

Studies on "Repeated Epilation" mouse mutant embryos: II. Development of limb, tail, and skin defects.

The present paper reports the development of limbs, tail, and skin abnormalities in homozygous Repeated Epilation (Er/Er) mouse embryos. Defects can first be observed on day 13 and become fully expressed at 18-19 days of gestation (vaginal plug = day 1 of gestation). In 13-day-old embryos, the apical ectodermal ridge and some areas of the limb epidermis are unusually thickened. A similar hyperplasia affects the tail tip and the flank epidermis. Limb defects are located in the autopod. Both pairs of footplates are shortened and deformed; no separation occurs between the digits. Only the phalanges are involved; they may be joined together either by soft tissues or by cartilage. Hypophalangy affects the most distal phalanges. Nails are missing or poorly developed. At stage 13, the tail tip is bent over the dorsal side and becomes twisted; at later stages, the tail appears shortened. From the 14-day stage onwards, there is a progressive fusion between the limb, the body, and/or the tail epidermis. The embryological analysis of the abnormalities indicates that the thickened and rigid epidermis impedes the normal growth of the limb buds and of the tail. Our observations suggest that limb and tail defects observed in mice homozygous for the Repeated Epilation mutation may be secondary to primary changes occurring in the epidermis. Some malformations described in this paper closely resemble those observed in sm/sm (syndactylism) and pf (pupoid fetus) mouse embryos.

Animals↗

The effect of tail skin on the morphology and morphogenesis of limb regenerates in the red-backed salamander, Plethodon cinereus.

Tail skin cuffs have been grafted to the upper forelimb of red-backed salamanders in either normal or 180 degrees-rotated dorsoventral orientation. Subsequent amputation through the graft region resulted in arrested regeneration, distally deficient or typical four-digit regenerates. Distribution was not substantially influenced by graft orientation nor were there any supernumerary limbs induced by the axially dislocated tail skin on the limb stumps. Furthermore, regenerates bore no indication of tail-like structures other than large granular skin glands proximally. These data indicate that, unlike limb skin, tail skin is not morphogenetically active in the epimorphic process of limb regeneration. In addition, the species used in this study is a fin-less, round-tailed salamander. It is therefore suggested that the previously reported morphogenetic effects of tail skin on limb regeneration may be related to the presence of tail fins on the species studied.

Animals↗

Modulation of cell-cell adherens junctions by surface clustering of the N-cadherin cytoplasmic tail.

Cadherins mediate the formation of cell-cell adherens junctions (AJ) by homophilic interactions through their extracellular domains as well as by interacting with the actin cytoskeleton via their cytoplasmic portions. Cadherin clustering initiates cytoplasmic signaling that results in the assembly of structural components into cell-cell AJ. To elucidate the function of the cytoplasmic tail of cadherins in initiating the assembly signal, we generated and characterized a chimeric cadherin tail fused to an inert transmembrane anchor. The chimera enabled us to cluster the cadherin cytoplasmic tail in the absence of extracellular portions of the molecule. The transfected cadherin tail chimera localized to cell-cell AJ of epithelial cells, indicating that the submembrane junctional plaque has the capacity to recruit additional cadherins, with no involvement of their extracellular domains. Expression of the chimera in cells of mesenchymal origin resulted in dominant negative effects on the formation of cell-cell AJ. Surface clustering of cadherin cytoplasmic tails induced the recruitment of components and structural assembly of cell-cell AJ, thereby reversing the initial dominant-negative effects. We conclude that the cadherin cytoplasmic tail contains information required to direct the molecule to cell-cell AJ. Its function as modulator of cell-cell AJ depends on cell type and on whether the tail is clustered.

3T3 Cells↗

The 3'-tail of a forked-duplex sterically determines whether one or two DNA strands pass through the central channel of a replication-fork helicase.

DnaB helicase is a ring-shaped hexamer that unwinds DNA at a replication fork. To understand how this protein interacts with DNA during unwinding, DnaB from Thermus aquaticus was incubated with chemically modified forked-duplex DNA substrates and the unwinding rates were measured. Unwinding was inhibited by modifications made to the 5'-tail, but not the 3'-tail, suggesting that the helicase interacts with the 5'-tail but not the 3'-tail during unwinding. Using oligonucleotides of mixed polarity, it was confirmed that DnaB translocates in the 5' to 3' direction as it unwinds DNA. A substrate was synthesized that contained two duplexes in tandem. Experiments involving various modifications of this tandem duplex demonstrated that when the 3'-tail is short, two stands of DNA pass through the central channel of DnaB with no resultant unwinding. Thus, the role of the 3'-tail in stimulating unwinding has been elucidated. The 3'-tail does not bind to DnaB during unwinding, but sterically determines whether one or two DNA strands pass through the central channel of DnaB. Furthermore, a new substrate for DnaB locomotion has been discovered. DnaB may actively translocate in the 5' to 3' direction along single-stranded DNA, even when a complementary strand is also present within the protein's central channel. This new mode of action may regulate DnaB activity by inhibiting unwinding at regions of DNA that are not forked. Furthermore, this new function for DnaB may coordinate abortion of leading and lagging strand replication if a nick is encountered on the leading strand.

Bacterial Proteins↗