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PubMed1990

All-or-none craniorachischisis in Loop-tail mutant mouse chimeras.

Mouse embryos homozygous for the mutant gene Loop-tail (Lp) are characterized by craniorachischisis, an open neural tube extending from the midbrain to the tail. In the present study, experimental chimeric mice containing mixtures of genetically mutant (from Lp/+ x Lp/+ matings) and genetically normal cells were produced. Our aim was to determine whether a 'rescue,' phenotypic gradient, or intermediate expression (i.e. alternating areas of open and closed neural tube) would be observed in these chimeras. We report our analyses of Loop-tail mutant chimeras (n = 82) by gross examination, progeny testing and quantitative analysis of glucose phosphate isomerase (GPI) isozyme levels. An all-or-none craniorachischisis in Loop-tail mutant chimeras was observed. Two multicolored adult chimeras, without any gross evidence of a neural tube defect, were shown to be homozygous Loop-tail chimeras (Lp/Lp in equilibrium +/+) by progeny testing. These results indicate that the normal phenotype can be expressed in the presence of mutant cells. Conversely, six neonates with craniorachischisis were shown to be chimeras by GPI analyses. These results show that the full mutant phenotype can be expressed even when one-third to one-half of the cells are genotypically wild-type. This study did not determine which tissue is primarily responsible for the defective neurulation in this mutant, but suggests that a 'threshold' mechanism underlies the Loop-tail mutant phenotype. In some chimeras that threshold is not reached and the neural tube remains open, whereas in other chimeras the threshold is reached and the neural tube closes completely.

Animals↗
PubMed2003

Differential regulation of cell adhesive functions by integrin alpha subunit cytoplasmic tails in vivo.

Cell adhesion to fibronectin (FN) is crucial for early vertebrate morphogenesis. In Xenopus gastrulae, several distinct integrin-dependent adhesive behaviors can be identified: adhesion of cells to FN, assembly of FN fibrils, and initiation of cell spreading and migration in response to mesoderm inducing signals. We have taken a chimeric integrin approach to investigate the role of the integrin alpha cytoplasmic tail in the specification of these developmentally significant adhesive functions. Cytoplasmic tail-deleted alpha4 constructs and alpha4-ectodomain/alpha-cytoplasmic tail chimeras were generated and expressed in whole embryos. Normal gastrula cells lack integrin alpha4 and, correspondingly, are unable to adhere to the alpha4 ligand, the V-region of FN. The ability of alpha4 constructs to promote adhesive behaviors was established by placing tissue explants or dissociated cells on an FN V-region fusion protein that lacks the RGD (Arg-Gly-Asp)/synergy sites or treating whole embryos with antibodies that block endogenous integrin-FN interactions. We found that each alpha4 cytoplasmic domain deletion mutant and alpha-tail chimera examined could support cell attachment; however, activin induction-dependent cell spreading, mesoderm cell and explant motility, and the ability to assemble FN matrix on the blastocoel roof varied with specific alpha subunit tail sequences. These data suggest that alpha cytoplasmic tail signaling and changes in integrin activation state can regulate a variety of developmentally significant adhesive behaviors in both space and time.

Activins↗
PubMed2005

Cytosolic tail sequences and subunit interactions are critical for synaptic localization of glutamate receptors.

AMPA-type glutamate receptors mediate excitatory synaptic transmission in the nervous system. The receptor subunit composition and subcellular localization play an important role in regulating synaptic strength. GLR-1 and GLR-2 are the Caenorhabditis elegans subunits most closely related to the mammalian AMPA-type receptors. These subunits are expressed in overlapping sets of interneurons, and contain type-I PDZ binding motifs in their carboxy-terminal cytosolic tail sequences. We report that GLR-1 and GLR-2 may form a heteromeric complex, the localization of which depends on either GLR-1 or GLR-2 tail sequences. Subunit interactions alone can mediate synaptic localization as endogenous GLR-1, or GLR-2 subunits can rescue the localization defects of subunits lacking tail sequences. Moreover, GLR-2 cytosolic tail sequences are sufficient to confer synaptic localization on a heterologous reporter containing a single-transmembrane domain. The localization of this GLR-2 reporter requires both a PDZ-binding motif in the GLR-2 tail sequence, and sequences outside of this motif. The PDZ protein LIN-10 regulates the localization of the reporter through the sequences outside of the PDZ-binding motif. Our results suggest that multiple synaptic localization signals reside in the cytosolic tail sequence of the receptor subunits, and that channel assembly can rescue the synaptic localization defects of individual mutant subunits as long as there are also wild-type subunits in the receptor complex.

Amino Acid Motifs↗
PubMed2005

A three-amino-acid-long HLA-DRbeta cytoplasmic tail is sufficient to overcome ER retention of invariant-chain p35.

The p35 isoform of the human invariant chain (Iip35) contains an N-terminal RXR endoplasmic-reticulum (ER) retention signal that becomes nonfunctional only after assembly with MHC-class-II molecules. We have previously shown that the MHC-class-II beta-chain cytoplasmic tail is crucial for the maturation of class-II/Iip35 complexes. In order to shed some light on the molecular determinants involved in shielding the RXR motif, we performed site-directed mutagenesis of the DRbeta chain and Ii cytoplasmic domains. Chimeric beta chains with irrelevant cytoplasmic tails allowed the efficient transport of Iip35 out of the ER in transiently transfected HEK 293T cells. An alanine scan of the cytoplasmic tail of HLA-DRbeta confirmed that no specific motif is required to overcome ER retention. Surprisingly, a beta chain with a three-amino-acid-long cytoplasmic tail (Tyr-Phe-Arg) was sufficient to overcome the Iip35 RXR motif. Moreover, replacement of residues F231 and R232 with alanines created a cytoplasmic tail (Tyr-Ala-Ala) that allowed ER egress. Given the limited length of this tail, steric hindrance would only be possible if the Ii ER retention motif was close to the membrane in the first place. However, this is not likely because an Ii molecule with an internal cytoplasmic deletion bringing the RXR motif closer to the membrane is not retained in the ER, even in the absence of class-II molecules. These results suggest that MHC-class-II molecules overcome ER retention and prevent COPI binding to the Iip35 RXR motif through a mechanism distinct from steric hindrance by its beta chain.

Amino Acid Sequence↗
PubMed1993

The MHC class II-associated invariant chain contains two endosomal targeting signals within its cytoplasmic tail.

The oligomeric complex formed by major histocompatibility complex (MHC) class II alpha and beta chains and invariant chain (Ii) assembles in the endoplasmic reticulum and is then transported via the Golgi complex to compartments of the endocytic pathway. When Ii alone is expressed in CV1 cells it is sorted to endosomes. The Ii cytoplasmic tail has been found to be essential for targeting to these compartments. In order to characterize further the signals responsible for endosomal targeting, we have deleted various segments of the cytoplasmic tail. The Ii mutants were transiently expressed and the cellular location of the proteins was analyzed biochemically and morphologically. The cytoplasmic tail of Ii was found to contain two endosomal targeting sequences within its cytoplasmic tail; one targeting sequence was present within amino acid residues 12-29 and deletion of this segment revealed the presence of a second endosomal targeting sequence, located within the first 11 amino acid residues. The presence of a leucine-isoleucine pair at positions 7 and 8 within this sequence was found to be essential for endosomal targeting. In addition, the presence of this L-I motif lead to accumulation of Ii molecules in large endosomal vacuoles containing lysosomal marker proteins. Both wild type Ii and Ii mutant molecules containing only one endosomal targeting sequence were rapidly internalized from the plasma membrane. When the Ii cytoplasmic tail was fused to the membrane-spanning region of neuraminidase, a resident plasma membrane protein, the resulting chimera (INA) was found in endocytic compartments containing lysosomal marker proteins. Thus the cytoplasmic tail of Ii is sufficient for targeting to the endocytic/lysosomal pathway.

Amino Acid Sequence↗
PubMed1999

The scaling of acceleratory aquatic locomotion: body size and tail-flip performance of the california spiny lobster panulirus interruptus

Tail-flipping is a crucial escape locomotion of crustaceans which has been predicted to be limited by increased body mass (M(b)). Given isometric growth, one may predict that with growth event duration will decrease as M(b)(-)(1/3), translational distances will increase as M(b)(1/3), translational velocity will be independent of M(b), translational acceleration will decrease as M(b)(-)(1/3), angular displacement will be independent of M(b) and angular velocity and angular acceleration will decrease as M(b)(-)(1/3). We tested these hypotheses by examining the scaling of 12 morphological variables, five kinematic variables and six performance variables of tail-flipping by the California spiny lobster Panulirus interruptus. Growth approximated isometry, which validated the use of the proposed scaling hypotheses. For animals from 1 to 1000 g M(b), the predicted scaling relationships for tail-flip duration and translational distance and velocity variables were supported; however, translational acceleration performance was much better than predicted. Predictions for rotation and rotational velocity variables were not supported, while the rotational acceleration data closely matched the predicted relationship. The increase in tail-flip duration as predicted suggests that muscle shortening velocity decreases with growth; the sustained acceleration performance (similar to findings for shrimp and fish fast-starts) suggests that muscle force output may increase at a greater rate than predicted by isometry. The scaling of rotational acceleration indicates that the torque produced during the tail-flip scales with a mass exponent greater than 1. Comparison of the tail-flip performance of Panulirus interruptus with those of other crustacean species reveals a wide range in performance by animals of similar body size, which suggests that the abdominal muscle may show interesting differences in contractile properties among different species.

Journal Article↗
PubMedDate not supplied

An adenovirus linked to mortality and disease in long-tailed ducks (Clangula hyemalis) in Alaska.

An adenovirus was isolated from intestinal samples of two long-tailed ducks (Clangula hyemalis) collected during a die-off in the Beaufort Sea off the north coast of Alaska in 2000. The virus was not neutralized by reference antiserum against known group I, II, or III avian adenoviruses and may represent a new serotype. The prevalence of the virus was determined in live-trapped long-tailed ducks at the mortality site and at a reference site 100 km away where no mortality was observed. Prevalence of adenovirus antibodies in serum samples at the mortality site was 86% compared to 10% at the reference site. Furthermore, 50% of cloacal swabs collected at the mortality site and only 7% of swabs from the reference site were positive for adenoviruses. In 2001, no mortality was observed at either of the study areas, and virus prevalence in both serum and cloacal samples was low, providing further evidence that the adenovirus was linked to the mortality event in 2000. The virus was used to infect long-tailed ducks under experimental conditions and resulted in lesions previously described for avian adenovirus infections and similar to those observed in long-tailed duck carcasses from the Beaufort Sea. The status of long-tailed ducks has recently become a concern in Alaska due to precipitous declines in breeding populations there since the mid-1970s. Our findings suggest that the newly isolated adenovirus is a disease agent and source of mortality in long-tailed ducks, and thus could be a contributing factor in population declines.

Adenoviridae↗
PubMed2005

Internalization of gonadotropin-releasing hormone receptors (GnRHRs): does arrestin binding to the C-terminal tail target GnRHRs for dynamin-dependent internalization?

Activation of seven-transmembrane receptors is typically followed by desensitization and arrestin-dependent internalization via vesicles that are pinched off by a dynamin collar. Arrestins also scaffold Src, which mediates dynamin-dependent internalization of beta2-adrenergic receptors. Type I mammalian gonadotropin-releasing hormone receptors (GnRHRs) do not rapidly desensitize or internalize (characteristics attributed to their unique lack of C-terminal tails) whereas non-mammalian GnRHRs (that have C-terminal tails) are rapidly internalized and desensitized. Moreover, internalization of Xenopus (X) GnRHRs is dynamin-dependent whereas that of human (h) GnRHRs is not, raising the possibility that binding of arrestin to the C-terminal tails of GnRHRs targets them to the dynamin-dependent internalization pathway. To test this we have compared wild-type GnRHRs with chimeric receptors (XGnRHR C-terminal tail added to the hGnRHR alone (h.XtGnRHR) or with exchange of the third intracellular loops (h.Xl.XtGnRHR)). We show that adding the XGnRHR C-terminal tail facilitates arrestin- and dynamin-dependent internalization as well as arrestin/green fluorescent protein translocation, but Src (or mitogen-activated protein kinase/extracellular-signal-regulated kinase kinase) inhibition does not slow internalization, and h.XtGnRHR internalization is slower than that of the hGnRHR. Moreover, arrestin expression increased XGnRHR internalization even when dynamin was inhibited and h.Xl.XtGnRHR underwent rapid arrestin-dependent internalization without signaling to G(q/11). Thus, although the C-terminal tail can direct GnRHRs for arrestin- and dynamin-dependent internalization, this effect is not dependent on Src activation and arrestin can also facilitate dynamin-independent internalization.

Animals↗
PubMed1998

Contrasting internalization kinetics of human and chicken gonadotropin-releasing hormone receptors mediated by C-terminal tail.

The chicken gonadotropin-releasing hormone receptor (GnRH-R) is notable for having a cytoplasmic C-terminal tail, which is not present in the mammalian GnRH-Rs. We report here that the cytoplasmic tail mediates rapid agonist-promoted receptor internalization. The chicken GnRH-R mediated internalization of gonadotropin-releasing hormone (GnRH) agonist (125I[His5-D-Tyr6]GnRH) at a rate of 11.3%.min-1, compared with only 0.71 %.min-1 for the human GnRH-R. To determine whether the presence of the cytoplasmic tail was responsible for the more rapid internalization kinetics of the chicken GnRH-R we truncated the tail after the Ile336 residue (S337stop). Receptor-mediated internalization of GnRH agonist by the S337stop-chicken GnRH-R was much slower than in the wild-type chicken receptor, and was similar to the wild-type human GnRH-R (0.55 %.min-1). These data indicate that rapid agonist-promoted internalization of the chicken GnRH-R is mediated through elements in the cytoplasmic C-terminal tail, distal to or including Ser337 and suggests that elimination of the C-terminal tail during evolution of mammalian GnRH-Rs may be related to its effects on internalization.

Animals↗
PubMed1978

Acceleration and suppression of rats' responding to avoid foot shock and tail shock.

Signalled response-independent shocks were superimposed on rats' wheel-turn responding to avoid shock administered to their feet through a grid floor or to their tails through fixed electrodes. In Experiment I, a tone paired with response-independent foot shock increased responding in three of four rats; a tone paired with tail shock increased responding in only one of four rats and suppressed responding in two rats. In Experiment II, a tone presented randomly with respect to response-independent shock had no reliable effect on responding to avoid foot shock or tail shock. In Experiment III, tail shock and foot shock were compared in a within-subject design while the temporal pattern of responding during conditioned stimuli was recorded. Responding during the conditioned stimulus preceding foot shock was characterized by initial suppression of responding at tone onset, followed by increased responding just before response-independent shock. Responding was suppressed throughout the conditioned stimulus preceding tail shock. Foot shock elicited bursts of responding, but tail shock did not.

Journal Article↗
PubMed1987

Inhibition of sympathetic constriction of the ex vivo tail artery perfused with blood from rats given frusemide.

Blood was withdrawn at a constant rate from the cannulated carotid artery of an anaesthetized rat and perfused an ex vivo segment of tail artery cannulated at both ends and contained in an organ bath. Blood returned to the rat via a cannulated jugular vein. The tail artery was constricted and perfusion pressure increased by peri-arterial stimulation at 5 Hz for 5 s every 2 min. Intravenous frusemide (5 mg/kg) decreased the stimulation responses of the tail artery. Diuresis-induced volume losses after frusemide were circumvented by a urinary bladder-intravenous shunt. Frusemide-induced reduction of tail artery vasoconstrictor responses was not seen in nephrectomized rats nor in rats pretreated with indomethacin or saralasin. Indomethacin did not change responses already reduced by frusemide. Exogenous arachidonate or angiotensin II infused into the blood perfusing the tail artery did not alter stimulation responses. We conclude that intravenous frusemide administration to a rat reduces sympathetic vasoconstrictor responses of the ex vivo blood perfused tail artery segment by a diuresis-independent but prostaglandin and angiotensin II dependent release of another hormone from the kidney.

Angiotensin II↗
PubMed1992

Field immobilization of American martens (Martes americana) and short-tailed weasels (Mustela erminea).

Ketamine hydrochloride (KH) and a 5:1 combination of KH and xylazine hydrochloride (XH) were used successfully to immobilize short-tailed weasels (Mustela erminea) and American martens (Martes americana), respectively. Four adult male martens were intramuscularly injected with 30 to 82 mg/kg KH and 8.0 to 16.4 mg/kg XH. Three adult male short-tailed weasels were intramuscularly injected with 20.8 to 42.1 mg/kg KH. Mean (+/- SE) induction times for martens and short-tailed weasels were 1.8 +/- 0.2 min and 46 +/- 4.1 sec, respectively; recovery times were 100.4 +/- 19.3 min and 97.9 +/- 6.3 min, respectively. Heart rate was relatively constant among martens; however, respiration varied widely (21 to 122 breaths per minute). Marten body temperature decreased between 0 and 20 min post-recumbency. Short-tailed weasel heart rate and respiration decreased in response to sedation until slightly before arousal. Body temperature stabilized by 20 min post-recumbency. Two short-tailed weasels tremored slightly within 10 min of arousal. I conclude that KH and KH/XH are safe immobilizing agents for martens and short-tailed weasels, respectively.

Animals↗
PubMed2000

Methanogens and sulfate-reducing bacteria in oil sands fine tailings waste.

In the past decade, the large tailings pond (Mildred Lake Settling Basin) on the Syncrude Canada Ltd. lease near Fort McMurray, Alta., has gone methanogenic. Currently, about 60%-80% of the flux of gas across the surface of the tailings pond is methane. As well as adding to greenhouse gas emissions, the production of methane in the fine tailings zone of this and other settling basins may affect the performance of these settling basins and impact reclamation options. Enumeration studies found methanogens (10(5)-10(6) MPN/g) within the fine tailings zone of various oil sands waste settling basins. SRB were also present (10(4)-10(5) MPN/g) with elevated numbers when sulfate was available. The methanogenic population was robust, and sample storage up to 9 months at 4 degrees C did not cause the MPN values to change. Nor was the ability of the consortium to produce methane delayed or less efficient after storage. Under laboratory conditions, fine tailings samples released 0.10-0.25 mL CH4 (at STP)/mL fine tailings. The addition of sulfate inhibited methanogenesis by stimulating bacterial competition.

Colony Count, Microbial↗
PubMed2001

[Transition of soleus troponin I isoforms and atrophy of testis in tail-suspended rats].

Objective. To observe the transition time of soleus I (TnI) isoforms and to elucidate the relationship between soleus TnI transition and atrophy; and to analyze the time course between testis atrophy and soleus atrophy. Method. Eight groups of male rats were suspended for 3, 4, 5, 7, 14, 21, 28 and 42 d, respectively. Besides, three groups of female rats were suspended for 3, 4 and 5 d respectively. Wet and relative weights (wet weight/body weight) of testis and soleus were measured. The expression of TnI was observed by Western blot. Result. The relative weight of soleus of tail-suspended male rats decreased significantly after 4 d of suspension as compared with control. The degree of rats soleus atrophy in the first 14 d of suspension was greater than that after 14 d. The relative weight of testis showed the same change as that of soleus. There was no significant change in the relative weight of soleus in 4 d of tail-suspended female rats. The significant decrease in the relative weight of tail-suspended female rats began on the 5th day. The Western blot showed that the transition from slow skeletal TnI (ssTnI) to fast skeletal TnI (fsTnI) in the soleus occurred in 14 d of tail-suspension. Conclusion. The overt atrophy of tail-suspended male rats occurs on the 4th day. The soleus TnI transition from ssTnI to fsTnI is on the 14th day. It is suggested that the TnI is not the sensitive protein to gravity. The overt atrophy of female tail-suspended rats occurs at the 5th day. This indicated that the decrease in testosterone level may accelerate the atrophy of the soleus.

Animals↗
PubMed2001

[Protective effects of Chinese herb-compound on cellular immunological function (correction of funcion) in tail-suspended rats].

Objective. To observe the protective effects of two kinds of Chinese herb-compounds (Dan-huang-ci compound and Shen-chuan-shu compound) on cellular immunology in tail-suspended rats. Method. The rats were divided into: 1) normal control group; 2) tail-suspended group; 3) tail-suspended + Dan-huang-ci compound; and 4) tail-suspended + Shen-chuan-shu compound. Ability of lymphocyte proliferation and production of IL-2 in rats in the four groups were compared after 21 d. Result. The immunological function of tail-suspended control group decreased significantly as compared with normal control group. Shen-chuan-shu compound could improve immunological function of tail-suspended rats obviously. Conclusion. Shen-chuan-shu compound could enhance cellular immunological function in rats under simulated weightlessness.

Animals↗
PubMed2000

[Effects of tail suspension on learning and memory function of mice].

Objective. To study the effects of simulated weightlessness on learning and memory capability of the brain. Method. Accuracy fraction, error frequency and pass rate were observed among control, restrained control, tail suspended (TS) control, restrained, and tail suspended mice in square water maze tests. And latent period and error time were observed in control and 30 degrees tail suspension mice in step down test. Result. The indices did not change significantly during learning period. Accuracy fraction of tail suspended group was reduced significantly in the tests as compared with pretest values. In step down test, latent period and error time showed no difference between TS 5 h and 2 d in untrained mice, but shortened evidently after TS 2 d and prolonged after TS 7 d in trained mice, which suggested the degradation of learning and memory ability after TS 5 h and 2 d respectively. Conclusion. Acute tail suspension depressed brain's learning ability and quality, while tail suspension of 7 d and 12 d impaired the spatial memory in mice.

Animals↗
PubMed2002

[Effects of copper mine tailings on seed germination and seedling growth of five legumes species].

Through solution culture and soil culture experiments, effects of Tongling copper mine tailings on seed germination and seeding growth of five legumes species were studied in this paper. The results showed that the seeds of five legumes species could germinate in the normal and acidified tailings extracted solution, but germination percentage was lower than that under control. It indicated that tailings extracted solution had inhibition effect on seed germination, however, acidified tailings extracted solution promoted absorbing water of the seeds in early stage. In five amelioration substrates between tailings and soils, the tailings also inhibited seed germination of the five species. No dead seedlings of Glycine max, Phaseolus angularis, P. calacaratus were found within 70 days.

Copper↗
PubMed2001

Effects of estrogen on tail suspension-induced disuse atrophy in ovariectomized rats: evaluation of the expression of interleukin-6 mRNA in the femur.

It is known that estrogen deficiency results in osteoporosis in human and experimental animals. However, how this deficiency affects the development of disuse bone atrophy is not well understood. Recently, it has been reported that estrogen affects the production of cytokines such as interleukin 6 (IL-6) which acts as local bone-resorbing factor. We thus studied how estrogen deficiency caused by ovariectomy and estrogen supplements affects the expression of IL-6 mRNA in the femur of tail-suspended rats. Five-week old female Wistar rats were ovariectomized and divided into two groups. One group received an intramuscular injection of estradiol dipropionate once a week (OVX-E2 group), and the other received the vehicle alone (OVX group). After the third injection, the rats were subjected to tail suspension in metabolic cages for 1, 3, 5 and 7 days. The wet weight of femurs significantly decreased after day 3 of tail-suspension in the OVX group. However, no significant decrease was observed in the OVX-E2 group. The expression of IL-6 mRNA estimated by RT-PCR (reverse transcription coupled polymerase chain reaction) in the femur significantly increased on day 5 after tail suspension in the OVX group. In the OVX-E2 group, that level significantly decreased on day 1 after the commencement of tail suspension. During suspension the level tended to be lower than that in the OVX group, a significant difference being observed on days 5 and 7 of suspension. The present results suggest that estrogen administration to OVX rats prevents both IL-6 production in the femur and the development of disuse bone atrophy induced by tail suspension.

Animals↗