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PubMed1976

Rheology of fibrin clots. III. Shear creep and creep recovery of fine ligated and coarse unligated closts.

Creep and creep recovery of human fibrin clots in small shearing deformations have been investigated over a time scale from 24 to 10(4) s. Coarse, unligated clots and fine clots ligated by fibrinoligase in the presence of calcium ions were studied to suppliement previous data on coarse ligated and fine unligated clots. Stress was found to be proportional to strain up to at least a maximum shear strain (in torsion geometry) of 6.2%. The initial modulus (25 s after imposition of stress) is proportional to approximately the 1.5 power of concentration for fine ligated and coarse unligated clots. For fine unligated closts there is comparatively little creep subsequent to the initial deformation; ligation (in this case involving mostly the gamma chains) reduces the creep to nearly zero. For coarse unligated clots, there is substantially more creep under constant stress, and creep recovery is not complete. Ligation (in this case involving both camma and alpha chains) alrgely supresses the creep and causes the recovery to be complete. If the structure if fully formed before creep begins, tests of creep recovery by the Boltzmann superposition principle show adherence to linear visoelastic behavior for all four clot types. Otherwise, the Boltzmann test fails and the recovery is much less than calculated. For fine ligated clots, the observed recovery agrees well with that calculated on the basis of a dual structure model in which an additional independent structure is built up in the deformed state, so that the state of ease after removal of stress is a balance between two structures deformed in opposite senses. It is postulated that the coherence and elastic modulus of the fine ligated clot are largely due to steric blocking of long protofibrils with a high flexural stiffness. In the coarse clot, it is proposed that the structure involves extensive branching of thick bundles of protofibrils, which become permanently secured by the ligation of the alpha chains of the fibrin.

Blood Coagulation↗
PubMed2006

IKK antagonizes CD95 ligation-mediated apoptosis by regulating NF-kappaB activity.

The CD95 (Apo1/Fas)/CD95 ligand system plays pivotal roles in various aspects of immune regulation and function by triggering apoptosis. Besides the apoptosis signaling pathway, CD95 ligation also induces the activation of NF-kappaB. Previous studies suggest that IkappaB kinase (IKK) may be a key player in cell survival by mediating NF-kappaB activation. However, the roles of IKK in CD95 ligation-mediated apoptosis and NF-kappaB activation are still not clear. In this report, we show that expression of the caspase-resistant uncleavable IKKbeta (UCIKKbeta) mutant suppressed CD95 ligation-mediated cell death in HeLa cells. Furthermore, CD95 ligation induced much more cell death in IKKbeta-/- murine embryonic fibroblasts (MEFs) than in wild type MEFs, despite that IKK was only marginally activated upon CD95 ligation. Pretreatment of HeLa cells with a specific IKK inhibitor NEMO-binding domain (NBD) peptide blocked CD95 ligation-induced NF-kappaB transcriptional activity. And UCIKKbeta enhanced the basal NF-kappaB activity, and consequently led to higher NF-kappaB activity upon CD95 ligation in HeLa cells. Therefore, IKK antagonizes CD95 ligation-mediated apoptosis by regulating NF-kappaB activity.

Animals↗
PubMed1997

Maxillary perfusion during Le Fort I osteotomy after ligation of the descending palatine artery.

PURPOSE: Controversy exists regarding management of the descending palatine artery (DPA) during Le Fort I osteotomy. Some surgeons advocate preserving the DPA, and others ligate the vessels. The purpose of this study was to evaluate maxillary gingival blood flow (GBF) during Le Fort I osteotomy in a sample of patients with and without ligation of the DPA. PATIENTS AND METHODS: Using a prospective randomized clinical study, we enrolled a study sample composed of 34 patients undergoing Le Fort I osteotomy. The patients were randomly assigned to either study group 1 (16) (DPA ligated) or group 2 (18) (DPA preserved). To measure maxillary GBF during the operation, we used laser Doppler flowmetry (LDF). The predictor variable was status of DPA management (ligated or preserved). The outcome variable was change in GBF over time. RESULTS: (DPA). Before ligation (or simulated ligation) of the DPA, the mean GBF for groups 1 and 2 was 11.4 +/- 8.6 and 11.9 +/- 9.4 mL/min/100 g tissue, respectively (P = .88). After ligation of the DPA in group 1, the mean GBF was 10.0 +/- 7.7 mL/min/100 g tissue. At the corresponding time in group 2 (DPA preserved), the mean GBF was 12.6 +/- 9.4 mL/min/100 g tissue. The difference in mean GBF between groups 1 and 2 was not statistically significant (P = .43). CONCLUSION: There were no statistically significant differences in mean maxillary GBF between patients having the DPA ligated and those having the DPA preserved as measured using LDF during Le Fort I osteotomy.

Adolescent↗
PubMed1999

CO ligation intermediates and the mechanism of hemoglobin cooperativity.

Direct experimental resolution of the ligation intermediates for the reaction of human hemoglobin with CO reveals the distribution of ligated states as a function of saturation. At low saturation, binding of CO occurs with slightly higher affinity to the beta chains, but pairwise interactions are more pronounced between the alpha chains. At high saturation, the two chains tend to behave identically. The sequence of CO ligation reconstructed from the distribution of intermediates shows that the overall increase in CO affinity is 588-fold, but it is not distributed uniformly among the ligation steps. The affinity increases 16.5-fold in the second ligation step, 4.6-fold in the third ligation step, and 7.7-fold in the fourth ligation step. This pattern and the detailed distribution of ligated states cannot be immediately reconciled with the predictions of either the concerted allosteric model of Monod-Wyman-Changeux or the sequential model of Koshland-Nemethy-Filmer and underscore a more subtle mechanism for hemoglobin cooperativity.

Carbon Monoxide↗
PubMed2002

Human topoisomerase IIalpha possesses an intrinsic nucleic acid specificity for DNA ligation. Use of 5' covalently activated oligonucleotide substrates to study enzyme mechanism.

Despite the importance of topoisomerase II-mediated DNA ligation to the essential physiological functions of the enzyme, the mechanistic details of this important reaction are poorly understood. Because topoisomerase II normally does not release cleaved DNA molecules prior to ligation, it is not known whether all of the nucleic acid specificity of its cleavage/ligation cycle is embodied in DNA cleavage or whether ligation also contributes specificity to the enzyme. All currently available ligation assays require that topoisomerase II cleave the initial DNA substrate before rejoining can be monitored. Consequently, it has been impossible to examine the specificity of DNA ligation separately from that of scission. To address this issue, a cleavage-independent topoisomerase II DNA ligation assay was developed. This assay utilizes a nicked oligonucleotide whose 5'-phosphate terminus at the nick has been activated by covalent attachment to the tyrosine mimic, p-nitrophenol. Human topoisomerase IIalpha and enzymes with active-site mutations that abrogated cleavage activity ligated the activated nick by catalyzing the direct attack of the terminal 3'-OH on the activated 5'-phosphate. Results with different DNA sequences indicate that human topoisomerase IIalpha possesses an intrinsic nucleic acid specificity for ligation that parallels its specificity for DNA cleavage.

Antigens, Neoplasm↗
PubMed2004

Evaluation of methods of archwire ligation on frictional resistance.

The aim of the study was to investigate the effect of elastomeric type and stainless steel (SS) ligation on frictional resistance using a validated method. To assess the validity of the new test system to measure mean frictional forces, SS and TMA wires, each with dimensions of 0.017 x 0.025 and 0.019 x 0.025 inches, were used in combination with a self-ligating Damon II bracket or a conventional preadjusted edgewise premolar SS bracket without ligation. Four types of elastomeric module, purple, grey, Alastik or SuperSlick, and a pre-formed 0.09 inch SS ligature were then assessed as methods of ligation using preadjusted edgewise premolar SS brackets. The specimens were tested on a Nene M3000 testing machine, with a crosshead speed of 5 mm/minute and each test run lasted for 4 minutes. Each bracket/wire combination with each method of ligation was tested 10 times in the presence of human saliva and the mean frictional force was recorded. The mean frictional forces were compared using three-way analysis of variance. The Damon II self-ligating bracket and unligated conventional SS bracket produced negligible mean frictional forces with any of the wires tested. For the 0.017 x 0.025 SS, 0.019 x 0.025 SS or 0.019 x 0.025 inch TMA wires, SS ligatures produced the lowest mean frictional forces. With the 0.017 x 0.025 TMA wire, purple modules produced the lowest mean frictional force. There was no consistent pattern in the mean frictional forces across the various combinations of wire type, size and ligation method. Under the conditions of this experiment, the use of passive self-ligating brackets is the only method of almost eliminating friction.

Analysis of Variance↗
PubMed1986

Regulation of inter- and intramolecular ligation with T4 DNA ligase in the presence of polyethylene glycol.

Polyethylene glycol (PEG) stimulates ligation with T4 DNA ligase. In 10% (w/v) PEG 6,000 solutions, only intermolecular ligation is enhanced by monovalent cations, while both inter- and intramolecular ligation occur without their presence. Similar stimulation was also caused by divalent cations or polyamines in the PEG 6,000 solutions. Such properties of the ligase could be applied to control the extent of inter- and intramolecular ligation. Ligation with cations or polyamines in 10% PEG 6,000 solutions was effective for intermolecular ligation. Ligation without cations or polyamines in 6.0% to 10% PEG 6,000 solutions was effective for intramolecular ligation.

Calcium↗
PubMed2003

Canonical nucleosides can be utilized by T4 DNA ligase as universal template bases at ligation junctions.

T4 DNA ligase catalyzes the template-dependent ligation of DNA. Using T4 DNA ligase under specific experimental conditions, we demonstrate that each of the four canonical nucleosides, centrally located on a template molecule such that they flank the site of ligation, can direct the ligation of nucleic acids regardless of the identity of the terminal nucleosides being covalently joined. This universal templating capability extends to those positions adjacent to the ligation junction. This is the first report, irrespective of the ligation method used or the identity of the template nucleosides (including analogs), which shows that nucleosides can act essentially as universal templates at ligation junctions in vitro. The canonical nucleosides do, however, differ in their ability to template sequence- independent ligations, with thymidine and guanosine being equally effective, yet more effective than adenosine and cytidine. Results indicate that hybridization strength surrounding the ligation junction is an important factor. The implications of this previously undiscovered property of T4 DNA ligase with canonical nucleosides are discussed.

Bacteriophage T4↗
PubMed1994

Hypermutable ligation of plasmid DNA ends in cells from patients with Werner syndrome.

Werner Syndrome is a rare autosomal recessive disorder characterized by an increased cancer risk and by symptoms suggestive of premature aging. Cells from these patients demonstrate a typical pattern of chromosomal instability and a spontaneous hypermutability with a high rate of unusually large deletions. We have studied the in vivo DNA ligation in three lymphoblast cell lines from Werner syndrome patients and three from normal donors. In our host cell ligation assay we transfected linearized plasmid pZ189 and measured the amount of plasmid DNA ends rejoined by these host cells as the ability of the recovered plasmid to transform bacteria. A mutagenesis marker gene close to the ligation site allowed screening for mutations. Subsequent mutation analysis provided information about the accuracy of the ligation process. The cells from Werner syndrome patients were as effective as normal cells in ligating DNA ends. However, mutation analysis revealed that the three Werner syndrome cell lines introduced 2.4-4.6 times more mutations (p < 0.001) than the normal cell lines during ligation of the DNA ends: the mutation rates were 69.4, 97.2, and 58.7%, as compared to 23.6, 21.7, and 24.4% in the normal cell lines. These increased mutation frequencies in plasmids ligated during passage through Werner syndrome cells were mainly due to a significant (p < 0.001) increase in deletions. This error-prone DNA ligation might be responsible for the spontaneous hypermutability and the genomic instability in Werner syndrome cells and related to the apparently accelerated aging and high cancer risk in affected patients.

Cell Line↗
PubMed2000

Plant enzymes but not Agrobacterium VirD2 mediate T-DNA ligation in vitro.

Agrobacterium tumefaciens, a gram-negative soil bacterium, transfers DNA to many plant species. In the plant cell, the transferred DNA (T-DNA) is integrated into the genome. An in vitro ligation-integration assay has been designed to investigate the mechanism of T-DNA ligation and the factors involved in this process. The VirD2 protein, which is produced in Agrobacterium and is covalently attached to T-DNA, did not, under our assay conditions, ligate T-DNA to a model target sequence in vitro. We tested whether plant extracts could ligate T-DNA to target oligonucleotides in our test system. The in vitro ligation-integration reaction did indeed take place in the presence of plant extracts. This reaction was inhibited by dTTP, indicating involvement of a plant DNA ligase. We found that prokaryotic DNA ligases could substitute for plant extracts in this reaction. Ligation of the VirD2-bound oligonucleotide to the target sequence mediated by T4 DNA ligase was less efficient than ligation of a free oligonucleotide to the target. T-DNA ligation mediated by a plant enzyme(s) or T4 DNA ligase requires ATP.

Adenosine Triphosphate↗
PubMed1988

[Cerebroprotective action of naftidrofuryl oxalate. I: Prolongation of survival time and protection of cerebral energy metabolism in bilateral carotid artery-ligated mice].

The present study was designed to elucidate whether naftidrofuryl oxalate (LS-121) may exert a beneficial effect on survival time and cerebral energy metabolism of bilateral carotid artery (BCA)-ligated mice. Survival time of BCA-ligated mice ranged from 100 to 308 sec. Administration of 15, 45 and 100 mg/kg, i.p. and 100 mg/kg, p.o. LS-121 significantly prolonged the survival time. Cerebral adenosine triphosphate (ATP), creatine phosphate (CP) and glucose contents were markedly reduced at 2 min after BCA-ligation. Cerebral lactate content was increased by the ligation, whereas the pyruvate content was not altered. Pretreatment of mice with 15, 45 mg/kg, i.p. and 100 mg/kg, p.o. LS-121 suppressed BCA-ligation induced decrease in high-energy phosphates of the mouse brain. Ligation-induced decrease in glucose and increase in lactate content tended to be attenuated by the treatment with 45 mg/kg, i.p. LS-121. Time course of changes in metabolic variables altered by BCA-ligation with and without the pretreatment with 45 mg/kg, i.p. LS-121 showed a significant suppression of ligation-induced decrease in cerebral high-energy phosphates. The results suggest that LS-121 is beneficial for ischemic mouse brain energy metabolism, which may be related to the prolongation of the survival time.

Animals↗
PubMed2006

Ligation of the hairpin ribozyme in cis induced by freezing and dehydration.

Although reducing the temperature slows most chemical reactions, freezing can stimulate some reactions by mechanisms that are only partially understood. Here we show that freezing stimulates the self-ligation (circularization) of linear forms of the hairpin ribozyme (HPR) containing 2',3'-cyclic phosphate and 5'-OH termini. Divalent metal ions (M2+) are not required, but monovalent cations and anions at millimolar concentrations can have various effects on this reaction depending on the specific ion. Under optimal conditions, the observed rate of M2+-independent self-ligation reaches a peak (0.04 min(-1)) at -10 degrees C with a yield of -60% after 1 h. In contrast, no ligation occurs either at above 0 degrees C or in solutions that remain unfrozen when supercooled to subzero temperatures. Under freezing conditions, the cleavage-ligation equilibrium strongly favors ligation. Besides freezing, evaporation of the aqueous solvent as well as the presence of ethanol at levels of 40% or above can also induce M2+-independent HPR ligation at 25 degrees C. We argue that partial RNA dehydration, which is a common feature of freezing, evaporation, and the presence of ethanol, is a key factor supporting HPR ligation activity at both above- and below-freezing temperatures. In the context of the RNA world hypothesis, freezing-induced ligation is an attractive mechanism by which complex RNAs could have evolved under conditions in which RNA was relatively protected against degradation.

Base Sequence↗
PubMed1992

Epistaxis: efficacy of arterial ligation and long-term outcome.

Epistaxis is the most common otolaryngologic emergency requiring hospital admission. Patients with this disorder are usually managed conservatively beginning with the simplest mode of treatment with surgical arterial ligation being reserved for cases of failed nasal packing. The purpose of this retrospective review was to evaluate the efficacy of arterial ligation and document all of the complications secondary to these procedures, especially the minor complications secondary to transantral internal maxillary artery (IMAX) ligation. A total of 402 patients admitted to the Vancouver General Hospital between 1980-1990 with a primary diagnosis of epistaxis were the basis for this review. The hospital charts of those patients who underwent arterial ligation were reviewed. A phone questionnaire was directed to this group. External carotid artery (ECA) ligation was associated with a high rate of rebleeding (9/20-45%) during the 10 year follow-up period. IMAX ligation was an effective procedure for controlling epistaxis with a small number of rebleeds (3/29-10%). Although few major complications were noted in the IMAX ligation group, frequent minor complications were noted on prolonged follow-up. Despite this, patient satisfaction was very good in the IMAX ligation group.

British Columbia↗
PubMed1976

Effect of uterine artery ligation on ovulation in the rat.

Female rats were divided into six groups: (1) control, (2) one uterine artery (a.) ligated near the utero-tubal (U-T) junction, (3) one uterine a. ligated at the level of the cervix, (4) both uterine aa. ligated separately at the U-T junction, (5) both uterine aa. ligated separately at the cervix and (6) both uterine aa. tied with one ligature at the cervix. Segmental aa. were disrupted in all experimental groups except group 6. Animals were allowed to recover for ten days and killed the first metestrus thereafter. Number of eggs ovulated was determined by flushing the oviduct with saline solution and counting the ova. Control rats ovulated 5.0 +/- 0.4 eggs per ovary. Groups 2 and 3 had an increase in the number of eggs shed from the ovary on the non-ligated side. In contrast, a decrease in the number of ova shed occurred on the ligated side. When both aa. were ligated separately (groups 4 and 5), irrespective of location, a decrease in the number of eggs shed by both ovaries was evident. No effect was found when only one ligature was placed near the cervix (group 6). The data demonstrate that blood supply to the ovary via the uterine artery is essential for the full complement of eggs to be shed.

Animals↗
PubMed1993

Effects of maternal bilateral ureteral ligation on fetal development of kidney in rats: morphometrical changes in glomerular components.

Development of the glomerulus in fetal kidney was studied morphometrically following ligation of both ureters of pregnant rats. The ligation was performed on days 17, 19, and 21 of gestation, and autopsy was done 24 hr after each operation. The percentage volumes of the five glomerular components (epithelial cells, capillary, mesangium, glomerular basement membrane, and Bowman's space) were determined by point counting, and the surface area of glomerular basement membrane per unit volume of glomerulus was calculated by intercept counting. On fetal days 18, 20, and 22, percentage volume of Bowman's space in the fetuses from the ligated mothers was significantly smaller than that in the fetuses from sham-ligated mothers. On fetal days 20 and 22, surface area of glomerular basement membrane and glomerular capillary length per unit volume of glomerulus and percentage of glomerular capillary volume in the fetuses from the ligated mothers were significantly larger than those in the fetuses from sham-ligated mothers. These results suggest that maternal bilateral ureteral ligation induces an increase in filtration area of glomerulus in fetal kidney when the fetal kidney is functional.

Animals↗
PubMed1980

Comparison of rubber band ligation and haemorrhoidectomy for second- and third-degree haemorrhoids: a prospective clinical trial.

One hundred patients with second- or third-degree haemorrhoids were randomly allocated to haemorrhoidectomy (50) or rubber band ligation (50). Forty-two in each group presented with rectal bleeding; haemorrhoidectomy relieved 36 and rubber band ligation relieved 31 of this symptom. All patients had prolapsing haemorrhoids at presentation. One year after treatment 45 haemorrhoidectomy and 43 rubber band ligation patients were assessed. Haemorrhoidectomy relieved 44 of 45 patients and rubber band ligation relieved 34 of 43 (P < 0.05). Haemorrhoidectomy caused pain in all cases, lasting for more than 48 h in 35. Rubber band ligation was painless in 5 and produced pain for more than 48 h in 15. Mean time off work was 32 days for haemorrhoidectomy and 3 days for rubber band ligation (P < 0.001). Rubber band ligation as an outpatient procedure is an effective treatment for second- and third-degree haemorrhoids and should be considered before recourse to surgery.

Adult↗
PubMed1990

Anesthesia and pressor responsiveness in chronic bile-duct-ligated dogs.

Cardiovascular homeostasis is comprised under general anesthesia and in jaundice. Because surgery is often performed on jaundiced patients, it is not altogether surprising that the incidence of perioperative complications is higher in such patients than in nonjaundiced ones. In this study we assessed the potential synergistic effects of anesthesia and jaundice on cardiovascular responsiveness of chronic bile-duct-ligated dogs. Responsiveness to norepinephrine, angiotensin II and isoproterenol was determined before and after chronic bile-duct ligation or sham-operation while the dogs were conscious or under halothane, fentanyl or pentobarbital-sodium anesthesia. These data have shown that halothane- and barbiturate-induced anesthesia do not alter mean arterial blood pressure in unoperated dogs when compared with conscious dogs before laparotomy. Furthermore, these two agents did not modify the pressor, dilator and positive inotropic responses to intravenous infusions of norepinephrine, angiotensin II and isoproterenol. Fentanol, however, reduced mean arterial blood pressure and heart rate without influencing responsiveness to the three vasoactive agents. Blunted responsiveness in the chronic bile-duct-ligated dogs to the three vasoactive agents was observed without any marked changes in mean arterial blood pressure or heart rate. The same blunted responses observed in the conscious, chronic bile-duct-ligated dogs were also seen in the anesthetized, chronic bile-duct-ligated dogs. Halothane caused a marked hypotensive effect in the chronic bile-duct-ligated dogs that was not seen in the sham-operated dogs. Conscious and anesthetized sham-operated dogs responded in the same manner as the conscious and anesthetized dogs before ligation. (ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia↗
PubMed1996

Ligation-induced acute pancreatitis increases pancreatic circulating trypsinogen activation peptides.

Ligation of the common bile-pancreatic duct induces hyperamylasemia and acute pancreatitis in rats. Pancreatic morphologic changes include edema, acinar cell damage, and mild inflammation. The pathogenesis of acute pancreatitis in this model is not understood, but may involve altered secretion and intrapancreatic activation of acinar proteases. We hypothesized that trypsinogen activation, measured by the production of plasma and pancreatic trypsinogen activation peptides (TAP), occurs early in this model. We performed the following experiments: rats were prepared with (1) bile-pancreatic ducts ligated and (2) ducts dissected but not ligated (sham). Rats were killed after 6, 24, and 48 hr. Serum amylase was measured and histologic sections were analyzed for morphologic changes. TAP was measured in both serum and pancreatic tissue homogenates using a specific polyclonal. anti-TAP antibody in an enzyme-linked immunosorbant assay. After 6, 24, and 48 hr of bile-pancreatic duct ligation, hyperamylasemia and acute morphologic changes of acute pancreatitis were observed. Evidence of acinar cell destruction was not evident until 48 hr after ligation. Levels of serum and pancreatic tissue TAP were significantly elevated at both 24 and 48 hr after ligation compared to those of sham. We conclude that increased intrapancreatic trypsinogen activation occurs early in this form of experimental acute pancreatitis and that it occurs prior to evidence of acinar cell destruction. These data and observations support the possibility that intrapancreatic protease activation contributes to the pathogenesis of ligation-induced acute pancreatitis.

Acute Disease↗