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At least 1,621 records · Page 90Linked to original sources
PubMed1989

Quantitative measurement of motor activity during the immobility reflex elicited by clamping in developing rats.

The immobility reflex can be elicited in developing rats by clamping the neck. Quantitative measurement of motor activity during such clamp-induced immobility was made by placing the rats in a jiggle cage. These measurements showed that there are two stages in the ontogenic development of this reflex; from day 5 to day 25 the inhibition of motor activity increased with age; from day 30 to day 90 the inhibition of motor activity was substantially reduced. It is postulated that in the first stage immobility could facilitate carrying by the mother whereas the second stage, when immobility is not as profound, could be related to escape from predators. Older rats must be ready to run if other strategies such as freezing and camouflage fail to avoid an attack from the predator.

Aging↗
PubMed1984

Patency of anastomosed arteries and veins subjected to reapplication of microvascular clamps.

One hundred and two rat femoral vessels, both vein and artery, were transected and repaired with a standard technique. After a 30-minute observation period, vessel clamps were reapplied in a standardized manner. The repairs were reexplored at 2 weeks. The results demonstrated no serious reduction in vessel patency in the first period or at the 2 week exploration. Reapplication of vessel clamps after an initial flow period post anastomosis does not have a significant effect on vessel patency.

Animals↗
PubMed1990

Does prostaglandin E1 and superoxide dismutase prevent ischaemic spinal cord injury after thoracic aortic cross-clamping?

The beneficial use of prostaglandin E1 (PGE1) and superoxide dismutase (SOD) on the tolerance to ischaemia of the spinal cord was evaluated following thoracic aortic cross-clamping in dogs. Aside from spinally evoked somatosensory potential (SEP) by means of a bipolar epidural catheter, postoperative evaluation of motor deficits was used to determine the efficiency of pharmacological protection when compared with controls. The animals were divided into four groups. Group I (n = 12) served as controls. The dogs of Group II (n = 12) were treated with PGE1 (100 ng/kg/min) during clamping and the first hour after declamping. In the third group (n = 12) SOD was given as an intra-arterial bolus (1 mg/kg) prior to declamping which was followed by a continuous perfusion (0.4 mg/kg/min) into the carotid artery for 25 min. In Group IV (n = 12) the dogs were treated with a combination of PGE1 and SOD in the same manner as in Groups 3 and 4. Results after pharmacological protection were significantly better than controls. In Group I all animals but one (92%) were paraplegic, as were five in Group II (42%) and eight in Group III (67%). In contrast no dog in Group IV developed paraplegia. There was a close correlation of SEP and postoperative recovery. The group with combination therapy (PGE1 plus SOD) was characterised by a loss of the evoked potential for a mean of 15 min, the PGE1 group for 45.8 min and the SOD group for 58.5 min. While the control group was characterised by a loss of 72.7 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Alprostadil↗
PubMed1992

Non-invasive monitoring of cardiac output changes during aortic cross-clamping for infrarenal reconstruction--a new technique using suprasternal Doppler-derived cardiac output.

There is a significant morbidity and mortality associated with elective infrarenal aortic reconstruction. To examine the value of continuous cardiac output monitoring for predicting those at risk, 40 consecutive patients were monitored using Doppler-derived cardiac output. The anaesthetist was blind to all information from the monitor and managed the patients using standard techniques. In 28 patients there were no observed changes, while in seven, cardiac output rose after aortic cross-clamping. In five patients a fall in cardiac output occurred after cross-clamping. No cardiac events or cardiac deaths occurred in the 35 patients who showed a rise or no change in cardiac output. However, there were three cardiac events, including one cardiac death in the group of five patients in whom a fall in cardiac output was observed. It would appear that intraoperative non-invasive Doppler-derived cardiac output monitoring successfully predicts high-risk patients who would perhaps benefit from more intensive pre-, peri- and postoperative care.

Aged↗
PubMed1991

Cerebral haemodynamics during proximal aortic cross-clamping.

This study was carried out to examine cerebral blood flow, including the microcirculation and intracranial pressure during cross-clamping (XC) of the thoracic aorta in pigs. Blood flow in the internal carotid artery was measured by electromagnetic flowmetry. Cerebral microcirculation was studied by the laser Doppler technique, and intracranial pressure measured by applying a fibre optic pressure monitoring catheter in the same craniotomy. Maximal and mean blood flow velocity of the middle cerebral artery was recorded using a transcranial Doppler and cardiac output measured by thermodilution. The thoracic aorta was cross-clamped distal to the left subclavian artery for 30 min. During aortic XC the internal carotid artery blood flow increased 191% (p less than 0.05). Simultaneously mean and maximal blood flow velocity of the middle cerebral artery both increased 125% (p less than 0.01). Intracranial pressure increased 163% (p less than 0.05), and there was an increase in cerebral flux of 23% (p less than 0.05). Within the first minutes following the release of XC, all values decreased to preocclusive values. In conclusion, we observed a significant increase in cerebral blood flow during XC of the thoracic aorta. This is in accordance with the finding of a simultaneous increase in cardiac output. These haemodynamic changes support the theory that an increased blood flow via the proximal feeding system to the anterior spinal artery might be important in avoiding neurological sequelae following proximal aortic XC.

Animals↗
PubMed2002

Can cerebral vasoreactivity predict cerebral tolerance to carotid clamping during carotid endarterectomy?

Cerebral vasoreactivity (CVR) was evaluated as a preoperative test in predicting cerebral tolerance to carotid clamping.A consecutive series of 115 carotid endarterectomy (CEA) cases were studied. Before surgical operation CVR was evaluated, by measuring the mean velocity of the middle cerebral artery (mv-MCA) using transcranial Doppler (TCD) at the basal condition and 20 min after intravenous administration of acetazolamide (1 g). CEA was performed under general anesthesia. TCD was used during surgery to evaluate mv-MCA and to calculate mv-MCA clamping/mv-MCA pre-clamping x100 ratio (mv-MCA%), which was used as the parameter to validate CVR.CVR did not correlate with mv-MCA% (r=0.22). There was no significant difference (P=0.09) between mean values of the non shunted subgroup and the shunted one.CVR does not seem to be suitable for evaluating cerebral tolerance to carotid clamping.

Acetazolamide↗
PubMed2002

A comparison between ischemic preconditioning, intermittent cross-clamp fibrillation and cold crystalloid cardioplegia for myocardial protection during coronary artery bypass graft surgery.

The aim of this study was to compare ischemic preconditioning (IPC) with two established methods of myocardial protection, namely cold crystalloid cardioplegia and intermittent cross-clamp fibrillation (ICCF), in coronary artery bypass graft (CABG) surgery. This was a prospective randomised study. Thirty CABG patients were randomised to receive: (a) St Thomas' cardioplegia solution no. 2; (b) ICCF; or (c) IPC (two 3-min periods of ischemia with 2-min of reperfusion). Surgery was performed under standardised conditions by one surgeon (WBP). The primary endpoint was cardiac troponin T release during the first 72 h after surgery. Mean troponin T at 72 h was significantly lower in the IPC group (0.5 microg/l; p=0.05, ANOVA) compared with the cardioplegia and ICCF groups (2.1 and 1.3 microg/l respectively). This suggests that ischemic preconditioning is superior at limiting myocardial necrosis during CABG, but there is no difference between cold crystalloid cardioplegia and intermittent cross-clamp fibrillation.

Aorta, Thoracic↗
PubMed2003

Endoluminal aortic shunting for distal perfusion during thoracic aortal cross-clamping in a pig model.

PURPOSE OF THE STUDY: To investigate the haemodynamic properties of a direct endovascular aortic shunt to maintain distal aortic perfusion as an alternative of a distal shunt (left-left-, Gott shunt) in thoracic aortic aneurysm repair. METHODS: A shunt was developed and tested in an in vitro model which should be capable of transporting a flow of 3-4 L/min with a decrease in blood pressure < 20 mmHg. Thereupon the shunt was tested in an in vivo experiment in six pigs to assess the possibility of its use with normal distal blood pressure. The shunt was inserted in the thoracic aorta and stayed in place for 1.5 h. Parameters were measured at six time intervals to assess organ perfusion, -function, cardiac output, proximal- and distal blood pressure and aortic- and shunt flow. PRINCIPLE FINDINGS: The mean blood flow through the shunt was 2.5 L/min. The difference of the mean blood pressure over the shunt was on average 14.20 mmHg. Parameters for coagulation disturbance and organ ischaemia were tested. The decrease in mean thrombocyte count was 299-158 (p<0.02). The venous lactate and the venous mesenteric lactate as parameters for intestinal ischemia did not increase significantly. No significant changes occurred in angiotensin II levels. Pulsatile flow was maintained but significantly suppressed (60%) distal from the shunt. The clamp time needed to insert the shunt and the venous mesenteric lactate, as well as the venous lactate, showed high correlation, r(s) = 0.9 (p<0.05) and r(s) = 0.94 (p<0.01). This also accounted for the 2nd clamp time, both r(s) = 0.95 (p<0.05). CONCLUSION: The shunt is capable of transporting a blood flow of 2-4 L/min with an acceptable decrease in distal blood pressure. However, the time, needed to insert the shunt, was significantly associated with parameters of organ ischaemia.

Anastomosis, Surgical↗
PubMed2001

Does temporary clamping of drains following knee arthroplasty reduce blood loss? A randomised controlled trial.

In a randomised, blinded study 76 patients undergoing primary total knee arthroplasty were assigned to either immediate drain opening (n = 45) or drains opened at 2 h (n = 31). No significant differences were found between the groups for the volume of drained blood, transfusion requirements, knee motion or wound status. The authors conclude that the practice of clamping drains has no benefit in routine knee arthroplasty. However, when faced with immediate brisk blood loss, the results suggest that drains can be clamped without any excess morbidity.

Arthroplasty, Replacement, Knee↗
PubMed2000

Aortocoronary bypass grafting: a comparison of HTK cardioplegia vs. intermittent aortic cross-clamping.

OBJECTIVE: Intermittend, hypothermic aortic cross-clamping (IAC) with myocardial fibrillation and cardioplegic arrest (CA) have been established both as effective methods for coronary artery bypass surgery (CABG). Nevertheless, there exists controversy about the more beneficial cardioprotective effect of one of these procedures in CABG-patients. METHODS: In this prospective study we compared the clinical outcome, ischemic serum-markers (CK, CK-MB, Troponin I), electrocardiogram (ECG)-changes, and hemodynamic data of 103 patients. Randomization in group I (IAC; n=52) or group II (CA; n=51) was done consecutively, all data were compared by Student's t-test or chi(2)-test and P<0.05 was regarded as significant. The Bretschneider-HTK solution was used for cardioplegic arrest. Data were collected before operation, before ischemic arrest, after 5 and 60 min of reperfusion, 1 and 6 h after operation, 1, 2 and 10 days postoperatively. RESULTS: There were no significant differences between both groups regarding general patient data: age (IAC: 64. 8+/-9.2 vs. CA: 63.8+/-9.0 years), left ventricular function (ejection fraction: IAC: 62+/-14 vs. CA: 64+/-13%), the amount of bypassed vessels (IAC: 3.4+/-0.5 vs. CA: 3.6+/-0.5), total bypass time (IAC: 113+/-31 vs. CA 108+/-20 min). The total time of ischemia was significantly less in the IAC group with 37+/-10 vs. 48+/-10 min in the CA group. In the IAC-group, a higher mortality was noticed (7. 7 vs. 3.9%; N.S.). This was combined with a significantly higher amount of patients with peak serum-values of CK-MB (>40 U/l) and troponin I (>50 ng/ml), 17 in the IAC-group (33%) vs. eight in CA-group (16%). Cerebral strokes were seen in two IAC-patients and none in CA-patients (NS). ECG-changes occurred in 22 IAC patients (42%) vs. 16 CA patients (31%); persistent ischemia related ECG-changes in six IAC (11.5%) vs. five CA-patients (9.8%). CONCLUSIONS: Both cardioprotective methods, IAC and HTK-cardioplegia, seem to offer sufficient myocardial protection in normal CABG-procedures. Although neurologic disorders and mortality rates were higher in patients with intermittent aortic cross-clamping, the differences to the cardioplegia group were not significant. According to the analysis of increased ECG-changes, higher CK-MB and troponin I values, which occurred especially in patients with myocardial ischemia time longer than 40 min, we conclude that cardioplegic arrest with HTK seems to offer more beneficial effects in procedures with prolonged ischemia.

Aged↗
PubMed1998

Single-clamp repair of aneurysms of the descending thoracic aorta.

Ischemic injury of the spinal cord remains a serious threat during the surgical treatment of aneurysms of the descending and thoracoabdominal aorta. Time is the critical factor in preventing spinal cord injury. The author uses a single-clamp technique that is simple and limits distal dissection, heparin dosage, and cross-clamp time, thus reducing the risk of paraplegia.

Aortic Aneurysm, Thoracic↗
PubMed1995

Isoflurane versus sodium nitroprusside for the control of proximal hypertension during thoracic aortic cross-clamping: effects on spinal cord ischemia.

OBJECTIVE: This study was designed to compare the effects of isoflurane and nitroprusside on spinal cord ischemia when they are used to control proximal hypertension during thoracic aortic cross-clamping (TACC). DESIGN: Prospective, randomized, blinded experimental study. SETTING: Laboratory and animal research facility. PARTICIPANTS: Adult mongrel dogs. INTERVENTIONS: Two groups of eight dogs had TACC for 45 minutes. Proximal aortic, distal aortic, and cerebrospinal pressure was calculated as the distal mean pressure minus the CSF pressure. Group 1 received nitroprusside and group 2 received isoflurane to control proximal hypertension during cross-clamping. The dogs were neurologically evaluated 24 and 48 hours later by an observer blinded as to the study group. Spinal cord segments were obtained for histopathologic examination. MEASUREMENTS AND MAIN RESULTS: Distal perfusion pressure and spinal cord perfusion pressure were significantly higher in the isoflurane group (p < .005). At 24 hours, seven of eight dogs in group 1 had severe neurologic injury (ie, paraplegia), with the eight having mild neurologic injury. This is in contrast to group 2, where 6 of 8 dogs had either minimal or no injury, one had mild injury, and one had severe injury. Similar results were observed at 48 hours (p < .005). CONCLUSIONS: Isoflurane, when used to control proximal hypertension during TACC, produces a higher spinal cord perfusion pressure and is associated with a lower incidence of neurologic injury than nitroprusside in this canine model.

Animals↗
PubMed2004

Multiple myomas treated with a temporary, noninvasive, Doppler-directed, transvaginal uterine artery clamp.

A 43-year-old woman with menorrhagia, dysmenorrhea, and pelvic pain of several years' duration had a uterus enlarged by myomas to the size of a 16-week pregnancy. Her uterine arteries were noninvasively transvaginally identified and occluded for 6 hours with a clamp that was guided by audible Doppler ultrasound. Following removal of the clamp, blood flow in the uterine arteries returned immediately. Menorrhagia symptoms diminished. Three months following treatment, uterine volume decreased by 48.9%, and dominant myoma volume decreased by 77.2%.

Adult↗
PubMed1998

Nucleotide-dependent prereplicative complex assembly by Cdc6p, a homolog of eukaryotic and prokaryotic clamp-loaders.

Expression of the Cdc6 protein (Cdc6p) is essential for formation of prereplicative complexes at budding yeast replication origins. Analysis of mutations in the conserved nucleoside triphosphate (NTP)-binding site of Cdc6p described here suggests that NTPs are required both for the productive interaction of Cdc6p with replication origins during G1 and the quantitative loading of the Mcm2-7 family of proteins onto chromatin. We show that Cdc6p exhibits significant sequence similarity to subunits of eukaryotic and prokaryotic clamp-loaders, which load ring-shaped DNA polymerase processivity factors onto DNA in an analogous reaction. Similarities in both sequence and mechanism suggest that Cdc6p and the clamp-loaders are members of a superfamily of nucleotide-dependent loading factors.

Alleles↗
PubMed1999

hMSH2-hMSH6 forms a hydrolysis-independent sliding clamp on mismatched DNA.

Mismatch recognition by the human MutS homologs hMSH2-hMSH6 is regulated by adenosine nucleotide binding, supporting the hypothesis that it functions as a molecular switch. Here we show that ATP-induced release of hMSH2-hMSH6 from mismatched DNA is prevented if the ends are blocked or if the DNA is circular. We demonstrate that mismmatched DNA provokes ADP-->ATP exchange, resulting in a discernible conformational transition that converts hMSH2-hMSH6 into a sliding clamp capable of hydrolysis-independent diffusion along the DNA backbone. Our results support a model for bidirectional mismatch repair in which stochastic loading of multiple ATP-bound hMSH2-hMSH6 sliding clamps onto mismatch-containing DNA leads to activation of the repair machinery and/or other signaling effectors similar to G protein switches.

Adenosine Triphosphatases↗
PubMed2002

Pivotal role of the beta-clamp in translesion DNA synthesis and mutagenesis in E. coli cells.

The genetic information is continuously subjected to the attack by endogenous and exogenous chemical and physical carcinogens that damage the DNA template, thus compromising its biochemical functions. Despite the multiple and efficient DNA repair systems that have evolved to cope with the large variety of damages, some lesions may persist and, as a consequence, interfere with DNA replication. By essence, the damaged-DNA replication process (hereafter termed translesion synthesis or TLS) is a major source of point mutations and is therefore deeply involved in the onset of human diseases such as cancer. Recent identification of numerous DNA polymerases involved in TLS has shed new light onto the molecular mechanisms of mutagenesis. Here, we show that in vivo, both error-free and mutagenic bypass activities of the three DNA polymerases known to be involved in TLS in Escherichia coli (PolII, PolIV and PolV) strictly depend upon the integrity of small peptidic sequences identified as their beta-clamp binding motif. Thus, in addition to its crucial role as the processivity factor of the PolIII replicase, the beta-clamp plays a pivotal role during the TLS process.

DNA Damage↗
PubMed1976

Acute ultrastructural changes in the middle cerebral artery due to the injury and ischemia of surgical clamping.

Ultrastructural changes in the zone of clamping of the middle cerebral artery of the squirrel monkey are described after application of a surgical clip. The experimental model utilized has been widely applied to the study of cerebral ischemia and possibly has relevance to clamps applied to the cerebral vessels during neurosurgical treatment of patients with cerebrovascular disorders. The earliest changes within the arterial wall were found in the smooth muscle (media) and accompanying fasciculi of nerves. Changes within the nerve bundles were sufficiently advances following 4 hours of vascular clipping to suggest temporary or permanent impairment of neurogenic innervation of the cerebral vessels distal to the trunk of the vessel clipped.

Animals↗