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Biomedical subjects

T R Magee

Publications and source records attributed to T R Magee.

103 records · Page 6Linked to original sources
PubMed1992

The effect of diabetes mellitus on the outcome of angioplasty for lower limb ischaemia.

Angioplasty is an important tool in the armamentarium of the clinician dealing with atherosclerotic disease. Diabetic patients with occlusive disease pose special problems. Four hundred and twenty-five lesions were dilated in 370 patients. No difference in site was found when comparing the diabetic and non-diabetic groups (p less than 0.001), but a significant difference in indication for treatment was observed. Cumulative patency at 5 years for iliac lesions in non-diabetic patients was 61.2% and in diabetic patients was 35.6% (p less than 0.05), for superficial femoral and popliteal artery lesions in non-diabetic patients it was 49.7% and in diabetic patients it was 38.8% (NS). The need for subsequent surgical intervention (p less than 0.01) and risk of death (p less than 0.001) are both significantly greater in the diabetic group. This study shows that angioplasty is a technique that can be used with success in diabetic patients and if the indications for interventions are compared, diabetic patients do not worse.

Angioplasty, Balloon↗
PubMed1992

Transcranial Doppler measurement before and after carotid endarterectomy.

Carotid endarterectomy not only removes a source of emboli but significantly increases flow up the internal carotid artery (ICA). ICA flow and middle cerebral artery velocity (Vmca) measurements were made before, during and after endarterectomy in 40 consecutive patients. Mean ICA flow increased from 207 ml/min (95% confidence interval (CI) 136-259) to 388 ml/min (95% CI 348-428) (P < 0.001, Mann-Whitney U test) following endarterectomy. Despite this, Vmca did not rise significantly at the end of the procedure. By the first postoperative day Vmca rose to 55.3 cm/s (95% CI 47.6-62.4) (P < 0.025, ANOVA) only to fall preoperative values (46.0 cm/s (95% CI 40.0-52.1)) by 6 weeks. These results suggest that cerebral autoregulation takes time to adapt to the increased flow and pressure following endarterectomy, but has stabilized by 6 weeks.

Aged↗
PubMed1992

Prevention of malalignment during non-reversed femorodistal bypass.

A simple technique is described using a Doppler flowmeter to prevent malalignment of a vein graft during femorodistal reconstruction. In 63 non-reversed vein bypass grafts, this technique has been used and no evidence of malalignment has been found on subsequent completion arteriography.

Anastomosis, Surgical↗
PubMed1992

A 5-year review of carotid endarterectomy in a vascular unit using a computerised audit system.

BIPAS, a computerised vascular audit has been used to analyse the results of 203 carotid endarterectomies performed over a 5-year period in a vascular unit. In addition, all but two patients have been followed up with regular duplex scans. The indications and surgical techniques have remained similar over the study period though preoperative carotid arteriography is no longer considered essential and intraoperative monitoring with transcranial Doppler insonation is becoming routine. There were six perioperative deaths and 20 postoperative neurological defects. However, only three survivors had any long-term disability. It was not possible to identify any particular patients at high risk of perioperative stroke, although simultaneous major surgery and significant bilateral carotid endarterectomy seemed to be more hazardous. Routine follow-up using duplex scanning identified patients with late occlusion (5%) and restenosis (8%), but only three patients (1.5%) suffered a late stroke. Once the perioperative hazards of death and permanent stroke (4.4% in this series) have been overcome, carotid endarterectomy provides good protection against subsequent stroke.

Adult↗
PubMed1992

Should we palpate foot pulses?

UNLABELLED: Palpation of foot pulses is traditionally used to evaluate patients with arterial disease. This study investigated observer variation in assessment of pedal vessels by pulse palpation and Doppler auscultation. A series of 33 claudicant patients and five controls were examined by a consultant, registrar, SHO and nurse. Dorsalis pedis (DP) and posterior tibial (PT) pulses were palpated and were then examined by Doppler with measurement of systolic pressures. CONTROL GROUP: No disagreement in DP pulses. However, all observers agreed on the presence of a PT pulse in only 70% of limbs. Claudicants: There was better agreement in palpation of the DP pulse (all observers agreed in 67% of limbs), than the PT pulse (all agreed in 53%). This suggests that the DP pulse is easier to palpate than the PT (P less than 0.05). By contrast there was better agreement on Doppler signals from the PT artery, all agreed in 78% of limbs; compared with the DP artery, all agreed in 58% (P less than 0.01). Pressure measurements by the observers agreed to within +/- 0.15 in 88% of claudicant and 100% of control limbs. Pedal pulse palpation in patients with arterial disease is subject to substantial observer error. Doppler pressure measurement is preferable unless pulses are bounding.

Adult↗
PubMed1991

The value of duplex scanning with venous occlusion in the preoperative prediction of femoro-distal vein bypass graft diameter.

The diameter of the long saphenous vein has been shown to affect the outcome of femoro-distal bypass. Many surgeons regard a vein with a diameter of less than 3 mm as being unsuitable. The long saphenous vein was studied in 35 patients undergoing femoro-distal bypass. Diameter measurements of the vein were performed using an ATL duplex scanner at the groin, mid-thigh and knee. Measurements were performed preoperatively both at rest and with a venous occlusion cuff to dilate the vein, and subsequently at 7 days and 2 months after implantation. The mean diameter of the vein at the mid-thigh was 4.1 mm non-dilated, 5.1 mm with occlusion, 5.0 mm 7 days postoperatively and 5.2 mm at 2 months (ANOVA, p less than 0.05). The mean diameter of the vein at the knee was 3.9 mm non-dilated, 4.8 mm with occlusion, 4.8 mm at 7 days and 4.9 mm at 2 months after operation (ANOVA, p less than 0.025). In all five patients whose preoperative resting vein diameter at the knee or mid-thigh was less than 3 mm, preoperative dilatation occurred, such that the diameter became greater than 3 mm. These results suggest that by using a technique of venous occlusion at the time of pre-operative vein mapping, the functional diameter of the vein can be predicted and vein utilisation may be increased.

Aged↗
PubMed1991

Rifampin-resistant replication of pBR322 derivatives in Escherichia coli cells induced for the SOS response.

Replication of plasmid pBR322 in Escherichia coli cells normally requires RNA synthesis and thus is sensitive to rifampin, an inhibitor of RNA polymerase. In cells induced for the SOS response, however, derivatives of pBR322 were found to replicate in the presence of rifampin. This rifampin-resistant replication of pBR322 requires the insertion of certain sequences of DNA. The replication depends on recF+ and DNA polymerase I.

Chromosomes, Bacterial↗
PubMed1990

Vein marking through ultrasound coupling gel.

It is now common practice to mark the course of the long saphenous vein by duplex scanning prior to in situ or reversed vein bypass grafting. This poses the problem of how best to mark its course durably in the presence of the ultrasound coupling gel on the skin. Blind to two observers, 11 commonly available marking pens were applied to the skin through ultrasound coupling gel, the gel was removed and the skin cleaned using a spirit-based antiseptic solution. The observers then rated the pens in order of performance. We recommend "Pilot Super Color Marker", "Artline 70" and "Edding 3020 Surgical Skin Marker" for preoperative vein mapping. These pens allow rapid marking of the saphenous or other veins through ultrasound coupling gel at the time of duplex scanning, and the marks persist after surgical preparation of the skin.

Humans↗
PubMed1990

Requirement of RecBC enzyme and an elevated level of activated RecA for induced stable DNA replication in Escherichia coli.

During SOS induction, Escherichia coli cells acquire the ability to replicate DNA in the absence of protein synthesis, i.e., induced stable DNA replication (iSDR). Initiation of iSDR can occur in the absence of transcription and DnaA protein activity, which are both required for initiation of normal DNA replication at the origin of replication, oriC. In this study we examined the requirement of recB, recC, and recA for the induction and maintenance of iSDR. We found that recB and recC mutations blocked the induction of iSDR by UV irradiation and nalidixic acid treatment. In recB(Ts) strains, iSDR activity induced at 30 degrees C was inhibited by subsequent incubation at 42 degrees C. In addition, iSDR that was induced after heat activation of the RecA441 protein was abolished by the recB21 mutation. These results indicated that the RecBC enzyme was essential not only for SOS signal generation but also for the reinitiation of DNA synthesis following DNA damage. recAo(Con) lexA3(Ind-) strains were found to be capable of iSDR after nalidixic acid treatment, indicating that the derepression of the recA gene and the activation of the elevated level of RecA protein were the necessary and sufficient conditions for the induction of iSDR.

DNA Replication↗
PubMedDate not supplied

Presence of NMDA receptor subunits in the male lower urogenital tract.

Some sexual responses in the male rat, specifically penile erection, are controlled by neural circuits in the brain and spine that are stimulated by the binding of excitatory amino acids (EAAs) to the postsynaptic N-methyl-D-aspartate receptor (NMDAR). In the hypothalamus, EAA/NMDAR interaction triggers the activation of neuronal nitric oxide synthase (nNOS) to produce nitric oxide (NO). The local synthesis of this neurotransmitter in the penile nerve terminals causes corpora cavernosal relaxation and erection. During sexual activity, NO is assumed to participate in seminal emission and ejaculation in the prostate and to inhibit voiding reflexes in the bladder. This study aimed to determine in vitro whether NMDAR is present in these organs and whether it affects the tone of tissue strips through an NO-dependent mechanism. We obtained penile, urinary bladder, and ventral prostate tissues from adult male rats and homologous surgical tissues from human male patients. We detected the NMDAR protein by Western blot and determined the binding of the NMDA antagonist, 3H-CGP. The NMDAR messenger ribonucleic acid (mRNA) was detected by reverse transcription/polymerase chain reaction and identified by cloning and sequencing. The in vitro response to NMDAR antagonists was measured in tissue strips that were precontracted with bethanechol or electrical field stimulation (in rat and human bladder), phenylephrine (in human corpora cavernosa), or norepinephrine (in human prostate). The NMDAR2B protein; ligand-binding activity; and NMDAR1, 2A, and 2B mRNAs were detected in all tissues studied. We found an NMDAR1 variant in rat prostate and penis and in human prostate that is larger than its cerebellar counterpart, but it encodes a 767-amino acid truncated protein (NMDAR1-T). The in vitro contraction of tissue strips was inhibited by NMDAR antagonists against the following sites: polyamine (with ifenprodil); ion channnel high affinity (with dizocilpine); ion channel low affinity (with memantidine, dextrometorphan, and ketamine); and, in an NO-independent, nonadrenergic-noncholinergic pathway that was only partially affected by EAAs. We conclude that, in vitro, all the essential NMDAR subunits are present in the lower urogenital tract, a novel variant of subunit 1 is expressed, the tissues bind an NMDAR ligand, and the NMDAR antagonists induce relaxation of tissue strips. Further work is necessary to determine whether the NMDAR subunits form a fully active receptor and participate in the control of organ tone that is relevant to male sexual activity.

Amino Acid Sequence↗
PubMedDate not supplied

Vein graft stenosis.

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Graft Occlusion, Vascular↗