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At least 379 records · Page 21Linked to original sources
PubMed1981

Solubilization of collagen-tailed acetylcholinesterase from chick retina: effect of different extraction procedures.

We have extracted acetylcholinesterase from young chick retinas by homogenization in different solutions combining high salt concentration, ionic and nonionic detergents, and EDTA, looking for an optimum procedure for the solubilization of collagen-tailed, asymmetric structural forms of the enzyme. High salt and EDTA seem to be the only necessary requirements for the solubilization of acetylcholinesterase as the A12 form (20S), and the presence of detergent in the homogenization medium does not significantly improve the yield of tailed enzyme. Extraction in the absence of detergent has the potential advantage of a threefold enrichment of tailed enzyme, because only about one-third of the total retinal acetylcholinesterase activity is solubilized. Divalent cations, especially Ca2+, seem to be involved in the attachment of the tailed enzyme to the retinal membranes, at the tail level. High salt-EDTA-extracted 20S acetylcholinesterase (without detergent) aggregates in the presence of exogenous Ca2+ and becomes "insoluble." However, the aggregated 20S acetylcholinesterase can be completely recovered and brought back into solution by further addition of EDTA. Besides, the aggregation can be prevented by the inclusion of Triton X-100 in the homogenization buffer or by adding the detergent concurrently with Ca2+. It is postulated that the acetylcholinesterase collagenous tail is coated by acidic lipid molecules hydrophobically bound to the tail protein so that Ca2+ ionic bridges would actually link these lipid molecules (and consequently the tail) to the membrane matrix. Removal of the lipid coat (e.g., by Triton X-100) produces tailed acetylcholinesterase molecules that no longer aggregate in the presence of Ca2+ and are fully accessible to collagenase digestion.

Acetylcholinesterase↗
PubMed1983

Calcium tail currents in voltage-clamped intact nerve cell bodies of Aplysia californica.

Calcium tail currents were measured in axotomized Aplysia neurones L2-L6 using a two-electrode voltage clamp and micro-electrodes of specially low resistance. Measurements were made at -40 mV following depolarizing pulses of 7 or 10 ms duration in the presence of 45 microM-tetrodotoxin and 200 mM-tetraethylammonium. Symmetrical currents were eliminated by addition of digitally stored current traces produced in response to equivalent hyperpolarizations. The remaining current, identified as a tail current, was blocked by replacement of extracellular calcium with cobalt or manganese. Computer fits showed that the tail current closely approximated the sum of two exponentially decaying components. The first had a time constant, tau 1, of 0.38 +/- 0.05 ms, which may have been frequency-limited by the speed of the clamp; the second had a time constant, tau 2, of 2.0 +/- 0.8 ms. A more slowly decaying third tail current component (tau 3 = 30 ms), which developed more slowly, may be related to the non-specific current rather than the calcium current. The tau 1 and tau 2 components of the tail current lost amplitude with increasing pulse duration along an approximately bi-exponential time course that resembled the time course of relaxation of the calcium current during a prolonged depolarization. The slow third component of the tail current showed no such inactivation. The amplitudes of the first and second components of the calcium tail current both increased as sigmoidal functions of the test pulse voltage, reaching half maximum at +20 mV and plateauing above +60 mV. The voltage dependencies of the two components were similar. The rate of decay of the tau 1 component increased with increasing temperature and with increasing negative potential, whereas tau 2 showed little dependence on these parameters. The rates of decay of neither the tau 1 nor the tau 2 component were affected by large changes in the amplitude of the test depolarization or in the amplitude of the tail current or by injection of calcium ions or EGTA. Thus, the kinetics of the tail current as resolved under our conditions appear to be virtually independent of calcium-mediated inactivation. Activation time constants (tau m) predicted from tau 1 are 3 to 5 times longer than the values of tau m determined from the half-time to peak of activation. These kinetics are slower than those reported for Limnaea by factors of 2.5 to 3.5.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1983

Inactivation of calcium conductance characterized by tail current measurements in neurones of Aplysia californica.

Calcium tail currents, recorded at -40 mV after repolarization from 7 or 10 ms voltage-clamp depolarizations in axotomized Aplysia neurones in the presence of tetrodotoxin and tetraethylammonium, were used to investigate the inactivation of the calcium conductance without interference from contaminating potassium currents. Prior depolarization with a prepulse (V1) resulted in a reduction in size of the tail currents recorded following the test pulse (V2). The reduction occurred in both the fast (tau 1 less than 0.4 ms) and slow (tau 2 approximately equal to 2.0 ms) components of the tail current. The degree of inactivation remained constant when tail currents were measured at potentials ranging up to 30 mV on either side of the potassium equilibrium potential. Thus, any changes in potassium current must have contributed virtually nothing to the changes in tail current amplitude seen following presentation of the prepulse. Inactivation was greatest following prepulses to potentials (+10 to +40 mV) that produce maximal entry of calcium ions, and declined to about zero as the prepulse approached the calcium equilibrium potential. For V1 potentials above +50 mV, the prepulse caused an apparent short-term facilitation of V2 tail currents in EGTA-injected neurones. This effect, detected up to 50 ms following the pulse, is of uncertain origin. Pressure injection of calcium ions caused reduction in the size of the tail current, which was restored by subsequent injection of EGTA. Tail current amplitude was reduced by presentation of the prepulse for all test pulse voltages, but the measured inactivation declined exponentially towards a minimum with test pulses of increasingly positive potential. Removal of inactivation following a 200 ms prepulse was greatly accelerated by injection of EGTA. The EGTA-resistant inactivation remaining at short times decayed with a time constant of about 0.12 s. The relation of tail current reduction to prepulse voltage is consistent with the interpretation that the EGTA-resistant inactivation remaining at short times depends on entry of calcium ions during the prepulse, as does the EGTA-sensitive inactivation remaining at later times. It is proposed that the 'EGTA-resistant' phase of inactivation results from loading of EGTA with calcium ions near the inner surface of the membrane during sustained calcium entry, allowing the intracellular calcium concentration to rise. The results provide further evidence for a calcium-mediated inactivation of the calcium conductance.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed2002

Importance of the cytoplasmic tails of the measles virus glycoproteins for fusogenic activity and the generation of recombinant measles viruses.

The generation of replication-competent measles virus (MV) depends on the incorporation of biologically active, fusogenic glycoprotein complexes, which are required for attachment and penetration into susceptible host cells and for direct virus spread by cell-to-cell fusion. Whereas multiple studies have analyzed the importance of the ectodomains of the MV glycoproteins hemagglutinin (H) and fusion protein (F), we have investigated the role of the cytoplasmic tails of the F and H proteins for the formation of fusogenic complexes. Deletions in the cytoplasmic tails of transiently expressed MV glycoproteins were found to have varying effects on receptor binding, fusion, or fusion promotion activity. F tail truncation to only three amino acids did not affect fusion capacity. In contrast, truncation of the H cytoplasmic tail was limited. H protein mutants with cytoplasmic tails of <14 residues no longer supported F-mediated cell fusion, predominantly due to a decrease in surface expression and receptor binding. This indicates that a minimal length of the H protein tail of 14 amino acids is required to ensure a threshold local density to have sufficient accumulation of fusogenic H-F complexes. By using reverse genetics, a recombinant MV with an F tail of three amino acids (rMV-FcDelta30), as well as an MV with an H tail of 14 residues (rMV-HcDelta20), could be rescued, whereas generation of viruses with shorter H tails failed. Thus, glycoprotein truncation does not interfere with the successful generation of recombinant MV if fusion competence is maintained.

Amino Acid Sequence↗
PubMed2002

Roles for the cytoplasmic tails of the fusion and hemagglutinin-neuraminidase proteins in budding of the paramyxovirus simian virus 5.

The efficient release of many enveloped viruses from cells involves the coalescence of viral components at sites of budding on the plasma membrane of infected cells. This coalescence is believed to require interactions between the cytoplasmic tails of surface glycoproteins and the matrix (M) protein. For the paramyxovirus simian virus 5 (SV5), the cytoplasmic tail of the hemagglutinin-neuraminidase (HN) protein has been shown previously to be important for normal virus budding. To investigate a role for the cytoplasmic tail of the fusion (F) protein in virus assembly and budding, we generated a series of F cytoplasmic tail-truncated recombinant viruses. Analysis of these viruses in tissue culture indicated that the cytoplasmic tail of the F protein was dispensable for normal virus replication and budding. To investigate further the requirements for assembly and budding of SV5, we generated two double-mutant recombinant viruses that lack 8 amino acids of the predicted 17-amino-acid HN protein cytoplasmic tail in combination with truncation of either 10 or 18 amino acids from the predicted 20-amino-acid F protein cytoplasmic tail. Both of the double mutant recombinant viruses displayed a replication defect in tissue culture and a budding defect, the extent of which was dependent on the length of the remaining F cytoplasmic tail. Taken together, this work and our earlier data on virus-like particle formation (A. P. Schmitt, G. P. Leser, D. L. Waning, and R. A. Lamb, J. Virol. 76:3953-3964, 2002) suggest a redundant role for the cytoplasmic tails of the HN and F proteins in virus assembly and budding.

Amino Acid Sequence↗
PubMed1998

Persistent interactions of core histone tails with nucleosomal DNA following acetylation and transcription factor binding.

In this study, we examined the effect of acetylation of the NH2 tails of core histones on their binding to nucleosomal DNA in the absence or presence of bound transcription factors. To do this, we used a novel UV laser-induced protein-DNA cross-linking technique, combined with immunochemical and molecular biology approaches. Nucleosomes containing one or five GAL4 binding sites were reconstituted with hypoacetylated or hyperacetylated core histones. Within these reconstituted particles, UV laser-induced histone-DNA cross-linking was found to occur only via the nonstructured histone tails and thus presented a unique tool for studying histone tail interactions with nucleosomal DNA. Importantly, these studies demonstrated that the NH2 tails were not released from nucleosomal DNA upon histone acetylation, although some weakening of their interactions was observed at elevated ionic strengths. Moreover, the binding of up to five GAL4-AH dimers to nucleosomes occupying the central 90 bp occurred without displacement of the histone NH2 tails from DNA. GAL4-AH binding perturbed the interaction of each histone tail with nucleosomal DNA to different degrees. However, in all cases, greater than 50% of the interactions between the histone tails and DNA was retained upon GAL4-AH binding, even if the tails were highly acetylated. These data illustrate an interaction of acetylated or nonacetylated histone tails with DNA that persists in the presence of simultaneously bound transcription factors.

Acetylation↗
PubMed1998

Poly(A) tail length control in Saccharomyces cerevisiae occurs by message-specific deadenylation.

We report that newly synthesized mRNA poly(A) tails are matured to precise lengths by the Pab1p-dependent poly(A) nuclease (PAN) of Saccharomyces cerevisiae. These results provide evidence for an initial phase of mRNA deadenylation that is required for poly(A) tail length control. In RNA 3'-end processing extracts lacking PAN, transcripts are polyadenylated to lengths exceeding 200 nucleotides. By contrast, in extracts containing PAN, transcripts were produced with the expected wild-type poly(A) tail lengths of 60 to 80 nucleotides. The role for PAN in poly(A) tail length control in vivo was confirmed by the finding that mRNAs are produced with longer poly(A) tails in PAN-deficient yeast strains. Interestingly, wild-type yeast strains were found to produce transcripts which varied in their maximal poly(A) tail length, and this message-specific length control was lost in PAN-deficient strains. Our data support a model whereby mRNAs are polyadenylated by the 3'-end processing machinery with a long tail, possibly of default length, and then in a PAN-dependent manner, the poly(A) tails are rapidly matured to a message-specific length. The ability to control the length of the poly(A) tail for newly expressed mRNAs has the potential to be an important posttranscriptional regulatory step in gene expression.

Exoribonucleases↗
PubMed2000

Role of histone N-terminal tails and their acetylation in nucleosome dynamics.

Histone N-terminal tails are central to the processes that modulate nucleosome structure and function. We have studied the contribution of core histone tails to the structure of a single nucleosome and to a histone (H3-H4)(2) tetrameric particle assembled on a topologically constrained DNA minicircle. The effect of histone tail cleavage and histone tail acetylation on the structure of the nucleoprotein particle was investigated by analyzing the DNA topoisomer equilibrium after relaxation of DNA torsional stress by topoisomerase I. Removal of the H3 and H4 N-terminal tails, as well as their acetylation, provoked a dramatic change in the linking-number difference of the (H3-H4)(2) tetrameric particle, with a release of up to 70% of the negative supercoiling previously constrained by this structure. The (H3-H4)(2) tetramers containing tailless or hyperacetylated histones showed a striking preference for relaxed DNA over negatively supercoiled DNA. This argues in favor of a change in tetramer structure that constrains less DNA and adopts a relaxed flat conformation instead of its left-handed conformation within the nucleosome. In contrast neither removal or hyperacetylation of H3 and H4 tails nor removal or hyperacetylation of H2A and H2B N-terminal tails affected the nucleosome structure. This indicates that the globular domain of H2A and H2B is sufficient to stabilize the tailless or the hyperacetylated (H3-H4)(2) tetramer in a left-handed superhelix conformation. These results suggest that the effect of histone tail acetylation that facilitates transcription may be mediated via transient formation of an (H3-H4)(2) tetrameric particle that could adopt an open structure only when H3 and/or H4 tails are hyperacetylated.

Acetylation↗
PubMed2000

Effects of histone tail domains on the rate of transcriptional elongation through a nucleosome.

The N-terminal tail domains of the core histones play important roles in gene regulation, but the exact mechanisms through which they act are not known. Recent studies suggest that the tail domains may influence the ability of RNA polymerase to elongate through the nucleosomal DNA and, thus, that posttranslational modification of the tail domains may provide a control point for gene regulation through effects on the elongation rate. We take advantage of an experimental system that uses bacteriophage T7 RNA polymerase as a probe for aspects of nucleosome transcription that are dominated by the properties of nucleosomes themselves. With this system, experiments can analyze the synchronous, real-time, single-passage transcription on the nucleosomal template. Here, we use this system to directly test the hypothesis that the tail domains may influence the "elongatability" of nucleosomal DNA and to identify which of the tail domains may contribute to this. The results show that the tail domains strongly influence the rate of elongation and suggest that the effect is dominated by the N-terminal domains of the (H3-H4)(2) tetramer. They further imply that tail-mediated octamer transfer is not essential for elongation through the nucleosome. Acetylation of the tail domains leads to effects on elongation that are similar to those arising from complete removal of the tail domains.

Amino Acid Sequence↗
PubMed2006

Physical methods used to study core histone tail structures and interactions in solution.

The core histone tail domains are key regulatory elements in chromatin. The tails are essential for folding oligonucleosomal arrays into both secondary and tertiary structures, and post-translational modifications within these domains can directly alter DNA accessibility. Unfortunately, there is little understanding of the structures and interactions of the core histone tail domains or how post-translational modifications within the tails may alter these interactions. Here we review NMR, thermal denaturation, cross-linking, and other selected solution methods used to define the general structures and binding behavior of the tail domains in various chromatin environments. All of these methods indicate that the tail domains bind primarily electrostatically to sites within chromatin. The data also indicate that the tails adopt specific structures when bound to DNA and that tail structures and interactions are plastic, depending on the specific chromatin environment. In addition, post-translational modifications, such as acetylation, can directly alter histone tail structures and interactions.

Binding Sites↗
PubMed1997

Reactivity of the isolated perfused rat tail vascular bed.

Isolated segments of the perfused rat tail artery display a high basal tone when compared to other isolated arteries such as the mesenteric and are suitable for the assay of vasopressor agents. However, the perfusion of this artery in the entire tail has not yet been used for functional studies. The main purpose of the present study was to identify some aspects of the vascular reactivity of the rat tail vascular bed and validate this method to measure vascular reactivity. The tail severed from the body was perfused with Krebs solution containing different Ca2+ concentrations at different flow rates. Rats were anesthetized with sodium pentobarbital (65 mg/kg) and heparinized (500 U). The tail artery was dissected near the tail insertion, cannulated and perfused with Krebs solution plus 30 microM EDTA at 36 degrees C and 2.5 ml/min and the procedures were started after equilibration of the perfusion pressure. In the first group a dose-response curve to phenylephrine (PE) (0.5, 1, 2 and 5 micrograms, bolus injection) was obtained at different flow rates (1.5, 2.5 and 3.5 ml/min). The mean perfusion pressure increased with flow as well as PE vasopressor responses. In a second group the flow was changed (1.5, 2, 2.5, 3 and 3.5 ml/min) at different Ca2+ concentrations (0.62, 1.25, 2.5 and 3.75 mM) in the Krebs solution. Increasing Ca2+ concentrations did not alter the flow-pressure relationship. In the third group a similar protocol was performed but the rat tail vascular bed was perfused with Krebs solution containing PE (0.1 microgram/ml). There was an enhancement of the effect of PE with increasing external Ca2+ and flow. PE vasopressor responses increased after endothelial damage with air and CHAPS, suggesting an endothelial modulation of the tone of the rat tail vascular bed. These experiments validate the perfusion of the rat tail vascular bed as a method to investigate vascular reactivity.

Animals↗
PubMed2006

Mutations in BMPR-IB and BMP-15 genes are associated with litter size in Small Tailed Han sheep (Ovis aries).

The Small Tailed Han is a prolific local sheep breed in China. The bone morphogenetic protein receptor IB (BMPR-IB) gene, which affects the fecundity of Booroola Merino sheep, and the bone morphogenetic protein 15 (BMP-15) gene, which affects the fecundity of Inverdale, Hanna, Belclare, Cambridge, and Lacaune sheep, were studied as candidate genes associated with the prolificacy of Small Tailed Han sheep. Single nucleotide polymorphisms of BMPR-IB and BMP-15 genes were detected in Small Tailed Han ewes (n = 188) by PCR-RFLP. The combined effect of the 2 genes on the prolificacy of Small Tailed Han sheep was studied. The results indicated that the same FecB mutation (Q249R) occurred in the BMPR-IB gene in Small Tailed Han ewes as found in Booroola Merino ewes. The Small Tailed Han ewes with genotypes FecB(B)/FecB(B) and FecB(B)/FecB(+) had 1.40 (P < 0.01) and 1.11 (P < 0.01) more lambs, respectively, than those with genotype FecB(+)/FecB(+). The same FecX(G) mutation (Q239Ter) of the BMP-15 gene was found in Small Tailed Han ewes as in Belclare and Cambridge ewes. The Small Tailed Han ewes with the heterozygous mutant FecX(G)/FecX(+) had 0.55 (P < 0.01) more lambs than those with the wild-type FecX(+)/FecX(+). The Small Tailed Han ewes carrying mutations in both BMPR-IB and BMP-15 genes had greater litter size than those with either mutation alone. In view of our results, marker-assisted selection using both BMPR-IB and BMP-15 genes is warranted to increase litter size in sheep and will be of considerable economic value to sheep producers.

Alleles↗
PubMed1997

Effect of bisphosphonate administration on the excretion of stress hormones in tail-suspended rats.

We demonstrated that administration of a bisphosphonate, YH529, prevents the development of disuse atrophy of the hind limbs induced by tail-suspension in rats. Since tail suspension is accompanied by an increase in the secretion of stress hormones, we studied whether administration of bisphosphonate affects the secretion of stress hormones during that procedure. Tail suspension was carried out in a metabolic cage by connecting a wire inserted through tail bone to the ceiling of the cage. The control rat received the same treatment but was not suspended. YH529 or a vehicle (PBS=phosphate buffered saline) was administered daily starting 3 days before the commencement of tail suspension. Urine samples were collected before the wire was inserted (day 0), on the day of insertion (day 1) and 3, 5 and 7 days after. In the control rats receiving PBS, urinary excretion of corticosterone and epinephrine did not change throughout the 7-day experimental period. In the control rats receiving YH529, urinary excretion of corticosterone increased significantly on the day of tail-piercing and wiring but then returned to the prior level. This increase was not observed in the control group receiving PBS. In the tail suspended rats, excretion of corticosterone and epinephrine increased significantly in both PBS and YH529 groups, the highest level being observed on the first day of tail suspension. Although statistically not significant, corticosterone excretion on day 1 of tail suspension was higher in the YH529 groups than that in the PBS group. It is thus suggested that administration of YH529 causes an augmented response to stress load.

Animals↗
PubMed1991

Glycocalyx of bodies versus tails of Schistosoma mansoni cercariae. Lectin-binding, size, charge, and electron microscopic characterization.

Infection with Schistosoma mansoni is initiated by penetration of the intact skin of the mammalian host with the head but not the tail of the parasite cercariae. The surface of cercariae is covered by a 1-2-micron thick carbohydrate-rich glycocalyx (gx). Furthermore, the transformation of cercariae to schistosomula (the next parasitic stage in the mammalian host) is associated with loss of gx from the bodies. To understand the role of gx in the host-parasite relationship, we have characterized the gx of both bodies and tails of S. mansoni cercariae. A fluorescent fucose-specific lectin-stained bodies and not tails of the organism. Moreover, when an enriched preparation of gx obtained by extraction with 40% aqueous phenol and exclusion from Sepharose CL-6B was subjected to affinity chromatography on insolubilized Lotus lectin, which binds fucose-containing glycans, only body gx was retained. Body gx is smaller and less negatively charged than tail gx. Electron microscopy showed that gx from bodies and tails is composed of 25-40-nm particles and fibrillar material. Carbohydrate composition of gx of bodies and tails indicate that fucose and glucose are major components, respectively. beta-Elimination experiments indicate that the linkage sugar is N-acetylgalactosamine in both cases. Upon treatment with alkaline borohydride, nearly 90% of gx of both bodies and tails was recovered as two glycan chains: I and II (Mr approximately 10,500 and 5,600, respectively). Glycan I was in both cases more negatively charged than glycan II. Fucose is the predominant sugar in glycan I of the bodies while glycan I of tails is mainly composed of glucose. The gx was resistant to several proteases. This resistance and the abundance of carbohydrate in gx may be of biological importance for survival of cercariae. The substantial differences observed between the gx of bodies and tails may provide the basis for understanding the mechanism of selective release of body gx during transformation.

Animals↗
PubMed1991

[A case of human tail].

A human tail is a rare anatomical curiosity. A case of a human tail associated with lipomyelomeningocele is reported. The made subject was born, by breech delivery, at the 39th-week with a 3,008 g body weight. He was admitted to our hospital because of the presence of a human tail and subcutaneous mass in the midline lumbosacral region. The tail was about 7.5 cm in length and 2 cm in diameter. It was elastic and covered by normal skin. No systemic anomaly was found. Spina bifida below L5 was revealed, and no bony shadow was found on the plain X-ray film. CT scan showed a low density area in the spinal canal between L3 and lower sacral region that extended into the tail through the spina bifida. MRI also revealed intraspinal long T2 mass which was attached to the spinal cord and extended into the tail. Myelogram indicated intradural extramedullary mass below the L3 level. Surgical treatment was performed on the 3rd month of life with a diagnosis of a human tail with lipomyelomeningocele. At surgery, the tail was found to consist mainly of lipomatous tissue which extended subcutaneously and entered the spinal canal through the spina bifida. The tail and subcutaneous lipomatous tissue were totally excised. The capsule of subcutaneous lipomatous tissue was followed circumferentially down into the spinal canal, and found to be transformed to arachnoid membrane. Intradural lipomatous tissue was excised piece by piece, leaving only a small remnant attached to the conus medullaris to preserve sacral nerve root function.(ABSTRACT TRUNCATED AT 250 WORDS)

Child, Preschool↗
PubMed1991

Different mechanisms mediating tail-flick inhibition induced by beta-endorphin, DAMGO and morphine from ROb and GiA in anesthetized rats.

The effects of beta-endorphin, D-Ala2-NMePhe4-Gly-ol-enkephalin (DAMGO) and morphine microinjected into raphe obscurus nucleus (ROb) and gigantocellular reticular nucleus alpha (GiA) in inhibiting the tail-flick response were studied in pentobarbital anesthetized rats. beta-Endorphin (0.1-3 micrograms) microinjected into ROb inhibited the tail-flick response dose-dependently and produced 100% inhibition at high doses (greater than 3 micrograms). DAMGO [0.004-0.015 micrograms] injected into ROb, also dose-dependently, inhibited the tail-flick response but reached a plateau of 60 to 80% inhibition at high doses (greater than 0.015 micrograms). Morphine (10-60 micrograms) injected into ROb produced only a small inhibition (less than 20% inhibition) even at high doses (greater than 60 micrograms). The rank order of potency of these opioids on the tail-flick inhibition was DAMGO greater than beta-endorphin greater than morphine. Morphine (1-10 micrograms) and DAMGO (0.004-0.03 micrograms) microinjected into GiA produced dose-dependent inhibitions of the tail-flick response and high doses of these two mu agonists fully inhibited the tail-flick response. However, beta-endorphin (0.1-10 micrograms) injected into GiA produced a small but dose-dependent inhibition of the tail-flick response (less than 60% inhibition). The rank order of potency of these opioids on the tail-flick inhibition was DAMGO greater than beta-endorphin greater than morphine. The inhibition of the tail-flick response induced by beta-endorphin (2 micrograms) microinjected into ROb was blocked by the coadministration of beta-endorphin-[1-27] (6 micrograms), but not naloxone (1 microgram).(ABSTRACT TRUNCATED AT 250 WORDS)

Analgesia↗
PubMed1987

Translocation of Escherichia coli recA protein from a single-stranded tail to contiguous duplex DNA.

Duplex DNA with a contiguous single-stranded tail was nearly as effective as single-stranded DNA in acting as a cofactor for the ATPase activity of recA protein at neutral pH and concentrations of MgCl2 that support homologous pairing. The ATP hydrolysis reached a steady state rate that was proportional to the length of the duplex DNA attached to a short 5' single-stranded tail after a lag. Separation of the single-stranded tail from most of the duplex portion of the molecule by restriction enzyme cleavage led to a gradual decline in ATP hydrolysis. Measurement of the rate of hydrolysis as a function of DNA concentration for both tailed duplex DNA and single-stranded DNA cofactors indicated that the binding site size of recA protein on a duplex DNA lattice, about 4 base pairs, is similar to that on a single-stranded DNA lattice, about four nucleotides. The length of the lag phase preceding steady state hydrolysis depended on the DNA concentration, length of the duplex region, and the polarity of the single-stranded tail, but was comparatively independent of tail length for tails over 70 nucleotides in length. The lag was 5-10 times longer for 3' than for 5' single-stranded tailed duplex DNA molecules, whereas the steady state rates of hydrolysis were lower. These observations show that, after nucleation of a recA protein complex on the single-stranded tail, the protein samples the entire duplex region via an interaction that is labile and not strongly polarized.

Adenosine Triphosphate↗
PubMed1976

The correlation between antinociceptive activity of narcotics and their antagonists as measured in the mouse tail-flick test and increased synthesis of brain catecholamines.

The effects of several narcotics, narcotic antagonists-analgesics and narcotic antagonists on the synthesis of dopamine and norepinephrine in mouse brain were estimated and related to their activity in the tail-flick test. Catecholamine synthesis was estimated by measuring the accumulation of 3H-dopamine and 3H-norepinephrine formed from an injection of 3H-tyrosine. Morphine produced dose-related increases in both tail-flick activity and catecholamine synthesis. Each of the narcotic analgesics produced a significant increase in catecholamine synthesis 30 minutes after the subcutaneous injection of an antinociceptive dose (ED80). Under these same conditions, drugs which are inactive in the tail-flick test, such as pentazocine, produced a decrease in catecholamine synthesis and cyclazocine; naloxone and naltrexone were without significant effect. However, cyclazocine, which was inactive in the tail-flick test and did not alter catecholamine synthesis 30 minutes after administration, demonstrated tail-flick activity and produced increased catecholamine synthesis 2 minutes after its administration. Morphine was devoid of either activity 2 minutes after administration. Similarly, at 2 hours after the administration of a dose of morphine (10 mg/kg) that was active in the tail-flick test and increased catecholamine synthesis at 30 minutes, neither tail-flick activity nor increased catecholamine synthesis was observed. Naloxone blocked both the antinociceptive action and the increased catecholamine synthesis produced by both morphine and methadone. The results of these studies indicate that a correlation exists between tail-flick activity of narcotic-like drugs and their ability to increase catecholamine synthesis. These data support the hypothesis that brain catecholamines may be involved in the central mediation of the tail-flick response and other actions of the narcotic analgesics.

Analgesics, Opioid↗