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Biomedical subjects

N Davies

Publications and source records attributed to N Davies.

At least 55 records · Page 3Linked to original sources

Totally endoscopic Ivor Lewis esophagectomy.

Esophagectomy is associated with significant risks of perioperative morbidity and mortality, as well as prolonged convalescence due to effects of the incisions used for conventional surgical access. Because the outcome of this procedure is palliative in the majority of patients, it is possible that laparoscopic techniques could improve initial postoperative outcomes and therefore make surgery more acceptable for patients with esophageal cancer. A new technique is described for Ivor Lewis esophagectomy, which incorporates a hand-assisted laparoscopic approach for gastric mobilization and a thoracoscopic approach for esophageal dissection and anastomosis. Initial experience in two patients has been encouraging, with postoperative hospital stay and convalescence shortened.

Adenocarcinoma↗

Determining the source of individuals: multilocus genotyping in nonequilibrium population genetics.

Recently founded populations represent an enormous challenge for genetic analysis: new populations are often genetically impoverished, making it hard to find sufficiently variable markers, and what little variation is present tends to be ancestral, rendering phylogenetic methods inappropriate. Recently, novel genetic markers and new statistical analyses have made multilocus genotyping an invaluable tool in the fledgling field of nonequilibrium population genetics. Such advances are not of mere academic interest but address questions of great economic, medical and conservation significance.

Journal Article↗

Altering the pattern of panretinal photocoagulation: could the visual field for driving be preserved?

PURPOSE: To identify the area of retina required to provide the visual field for driving and to investigate whether the pattern of panretinal photocoagulation (PRP) for proliferative diabetic retinopathy could be altered to avoid treatment in this area whilst leaving the total number of burns constant. METHODS: A mathematical model of the emmetropic eye is used to calculate retinal dimensions corresponding to different angles of visual field. These are used to define retinal regions that correspond to the UK DVLC visual field criteria and regions that lie outside this area. Further calculation estimates the number of laser burns applied within these regions for both 500 microns and 200 microns diameter spot sizes and various burn spacings. RESULTS: Modelling of the number of burns applied in the normal pattern of PRP agrees with the number required to control proliferative retinopathy. Reducing burn spacing or extending treatment up to the ora serrata allows application of sufficient burns to control the disease without encroaching on areas of the retina that provide the driving field. CONCLUSION: It is theoretically possible to alter the pattern of PRP to avoid treatment in retinal areas concerned with the driving visual field whilst leaving the total number of burns constant. This suggests that a clinical trial of such a pattern PRP could be performed to assess adequate control of proliferative retinopathy along with preservation of the visual field required for driving.

Automobile Driving↗

Prospective randomized double-blind trial between laparoscopic Nissen fundoplication and anterior partial fundoplication.

BACKGROUND: In the operative management of gastro-oesophageal reflux, a balance must be achieved between adequate control of reflux and excessive dysphagia. The ideal technique is not known. A randomized study was performed to determine whether laparoscopic anterior fundoplication is associated with a lower incidence of postoperative dysphagia than laparoscopic Nissen fundoplication, while achieving equivalent control of reflux. METHODS: Patients presenting for laparoscopic antireflux surgery were randomized to undergo either a Nissen fundoplication (n = 53) or an anterior 180 degrees hemifundoplication (n = 54). Patients were blinded to which procedure had been performed, and follow-up was obtained by a blinded independent investigator. Standardized clinical grading systems were used to assess dysphagia, heartburn and patient satisfaction 1, 3 and 6 months after operation. Objective measurement of lower oesophageal sphincter pressure, oesophageal emptying time, distal oesophageal acid exposure and endoscopic healing of oesophagitis was also performed. RESULTS: Operating time was similar for the two procedures (58 min for the Nissen procedure versus 60 min for anterior fundoplication). Resting and residual lower oesophageal sphincter pressures were lower following anterior fundoplication (29 versus 18 mmHg, and 13 versus 6 mmHg), and oesophageal emptying times were faster (92 versus 116 s). Acid exposure times and ability to heal oesophagitis were similar. At 3 months' follow-up clinical outcomes were similar for the two procedures. At 6 months, however, patients who had undergone anterior fundoplication experienced significantly less dysphagia for solid food and were more likely to be satisfied with the clinical outcome. CONCLUSION: Laparoscopic anterior fundoplication achieved equivalent control of reflux, more physiological postoperative manometry parameters, and an improved clinical outcome at 6 months. Continued follow-up remains necessary to confirm the long-term efficacy of the partial fundoplication procedure.

Double-Blind Method↗

Patients' experiences of having an underwater seal chest drain: a replication study.

The nursing management of patients who have a chest drain in situ has received little attention. The findings of a single small-scale study previously indicated that such patients' needs for information are not always fully met and pain control is inadequate. This small-scale study was replicated to produce broadly similar findings in a second hospital 2 years later. Despite some differences in the approach to management it was apparent that patients were still not well prepared pre-operatively and there was scope for improving pain control. All the patients reported considerable discomfort and pain of moderate to severe intensity. The type of pain described is typical of deep somatic/visceral pain.

Activities of Daily Living↗

Good outcome from surgery for ampullary tumour.

BACKGROUND: Ampulla of Vater tumours are rare but usually resectable. There is debate as to the better surgical approach between the standard radical procedure, which provides adequate resection margins, and local resection, which may carry a lower mortality. This study reports the 16-year experience of a specialist unit with these tumours, and compares our results with that of recently published series. METHOD: A retrospective review of patients admitted with an ampullary tumour to the Hepatobiliary and Pancreatic Surgery Unit, Royal Adelaide Hospital, Adelaide, Australia, between January 1981 and April 1997. RESULTS: Twenty-five patients (13 men, 12 women) of median age 65 years were admitted with an ampullary tumour to the unit during this period. The most common presentation was obstructive jaundice. Multiple endoscopic biopsy was found to be very reliable in distinguishing between benign and malignant tumours. Five patients, all male, had benign neoplasms: three adenomas, one carcinoid and one gangliocytic paraganglioma. Transduodenal local excision was performed in four patients. One patient had a Whipple procedure resulting in the only in-hospital death at 3 months. Twenty patients had adenocarcinoma, of which 13 patients had a pancreaticoduodenectomy, two local excisions, two palliative bypasses, two were unfit for surgery and one declined surgery. The resectability rate was 88%, with no operative mortalities. The 5-year actuarial survival of patients who underwent radical resection was 49%. CONCLUSIONS: Proximal pancreaticoduodenectomy, preferably a pylorus-preserving procedure, is safe and effective in the treatment of ampullary carcinoma, with low operative mortality and good long-term survival. Local resection is only recommended for small benign tumours and for patients who may be unfit for radical surgery.

Adult↗

Bioinvasions of the medfly Ceratitis capitata: source estimation using DNA sequences at multiple intron loci.

The Mediterranean fruit fly, Ceratitis capitata, is a devastating agricultural pest that threatens to become established in vulnerable areas such as California and Florida. Considerable controversy surrounds the status of Californian medfly infestations: Do they represent repeated introductions or the persistence of a resident population? Attempts to resolve this question using traditional population genetic markers and statistical methods are problematic because the most likely source populations in Latin America were themselves only recently colonized and are genetically very similar. Here, significant population structure among several New World medfly populations is demonstrated through the analysis of DNA sequence variation at four intron loci. Surprisingly, in these newly founded populations, estimates of population structure increase when measures of subdivision take into account the relatedness of alleles as well as their frequency. A nonequilibrium, likelihood-based statistical test that utilizes multilocus genotypes suggests that the sole medfly captured in California during 1996 was introduced from Latin America and was less likely to be a remnant of an ancestral Californian population. Many bioinvasions are hierarchical in nature, consisting of several sequential or overlapping invasion events, the totality of which can be termed a metainvasion. Phylogenetic data from multilocus DNA sequences will be vital to understanding the evolutionary and ecological processes that underlie metainvasions and to resolving their constituent levels.

Alleles↗

Identification of novel ligands for the gabapentin binding site on the alpha2delta subunit of a calcium channel and their evaluation as anticonvulsant agents.

As part of a program to investigate the structure-activity relationships of Gabapentin (Neurontin), a number of alkylated analogues were synthesized and evaluated in vitro for binding to the Gabapentin binding site located on the alpha2delta subunit of a calcium channel. A number of other bridged and heterocyclic analogues are also reported along with their in vitro data. Two compounds showing higher affinity than Gabapentin were selected for evaluation in an animal model of epilepsy. One of these compounds, cis-(1S,3R)-(1-(aminomethyl)-3-methylcyclohexyl)acetic acid hydrochloride (19), was shown to be effective in this model with a profile similar to that of Gabapentin itself.

Acetates↗

Use of steroids, tocolytics and antibiotics in the management of preterm labour in Wales.

The management of preterm labour (PTL) remains contentious. Many regimes are used for the management of this common condition and in utero transfer of pregnant women to another unit is not unusual in British practice. Medical staff in the accepting unit may have little or no experience with one or more drug regimes used in this condition which used in isolation and in combination with others may have disastrous consequences for the mother. We have assessed the variation in practice for the management of preterm labour in all consultant-led obstetric units in Wales using a postal questionnaire. The percentage of units with written guidelines for the management of PTL was 40%. All units used corticosteroids although the regimes used varied. Fourteen of the 15 units used tocolytics. Ritodrine and nifedipine were the most frequently used tocolytics but there was much variation in practice. Only seven (46.7%) units used antibiotics and five of these were randomising women in PTL to the ORACLE study. Postal surveys may not reflect accurately what actually happens in clinical practice. These data demonstrate that there is no common policy for the management of PTL even in a relatively small region such as Wales. We would suggest that the development of a regional policy for the management of preterm labour would be a significant step forward in the management of this controversial, but important cause of neonatal morbidity and mortality.

Journal Article↗

Epidemiology of giardiasis in Tasmania: a potential risk to residents and visitors.

BACKGROUND: Giardia infection is an ongoing problem in Tasmania and occurs throughout the state. It has been postulated that part of the problem is the reservoir of infection in native animals which is suggested to contribute to infections in humans. To date, however, no detailed study on the epidemiology of giardiasis in Tasmania has been carried out. METHODS: Information regarding the prevalence of Giardia infection in humans and the risk of intrafamilial transmission was obtained from the Department of Community and Health Services and from the direct examination of human or animal fecal samples. RESULTS: Giardia has been found to be present in a wide range of native and domestic animals and in humans of all ages from all over the state. CONCLUSIONS: Giardiasis is endemic in Tasmania and poses a risk to locals as well as to visitors to the state, especially those who participate in wilderness activities such as bushwalking. These people must be aware of the possible risk of Giardia infection and should take precautionary measures to avoid infection.

Adolescent↗

Palliation of dysphagia from inoperable oesophageal carcinoma using Atkinson tubes or self-expanding metal stents.

Until recently, intubation for the palliation of malignant dysphagia has relied upon the insertion of a variety of plastic tubes. Self-expanding metal stents are reported to have a lower complication rate. We have compared the results of Atkinson tube insertion with self-expanding metal stents in patients with inoperable oesophageal carcinoma. From 1990 to 1994 Atkinson tubes were inserted for the palliation of dysphagia from oesophageal cancer, from 1994 onwards self-expanding metal stents were used. Complications, mortality and hospital stay were compared in both groups of patients. In all, 87 patients with inoperable oesophageal carcinoma were treated, 46 with an Atkinson tube and 41 with metal stents. Complications occurred at similar rates in both groups (56% Atkinson tubes, 44% metal stents). There was a significantly higher perforation rate associated with Atkinson tube insertion (8 patients, 17%) compared with metal stents (1 patient, 2.4%, P = 0.02, chi 2). The length of stay was also significantly higher in the Atkinson tube group (median 10 days) compared with the metal stent group (3 days, P < 0.01, Mann-Whitney U test). Mortality rates were similar in both groups. The use of metal stents for the palliation of dysphagia in inoperable oesophageal carcinoma results in a lower perforation rate and a reduced length of stay and they represent a significant advantage over Atkinson tubes.

Adult↗

The inhibition of cytochrome c oxidase by nitric oxide using S-nitrosoglutathione.

The effect of the free radical nitric oxide (NO) on the activity of isolated cytochrome sigma oxidase was investigated by using ferrocytochrome sigma as an electron donor, and the system SNOG/DTT, which produces a steady-state NO concentration similar to that expected to be found in vivo. The initial electron entry into the heme a/Cu a center and the initial rate of the electron transfer between the two hemes were not affected by the presence of NO. Under our conditions, the rate of inhibition of cytochrome c oxidase was found to be dependent both on the SNOG (NO concentration) and on the ferrocytochrome c concentration (electron entry rate). The data confirm that NO binds exclusively at the binuclear center, and that the NO binding in these conditions requires the presence of an intermediate populated only in turnover. Accordingly, we found that the rate of inhibition is directly related to the electron entry rate. In addition, a residual activity seems to be present in cytochrome c oxidase in the presence of nitric oxide, suggesting that NO can act as an electron acceptor to cytochrome c oxidase in the presence of oxygen.

Cytochrome c Group↗

5-HT2A receptor and bipolar affective disorder: association studies in affected patients.

The aim of this study was to investigate the possible involvement of genetic variation in serotonin receptors in the aetiology of bipolar affective disorder. The 5-HT2A receptor gene was systematically screened for genetic variants by single strand conformation polymorphism (SSCP) methods in subjects with bipolar affective disorder. Four polymorphisms (two structural changes, Thr25Asn and His4 M52Tyr, and two silent polymorphisms, 102-T/C and 516-C/T) which had previously been found in patients with schizophrenia and control subjects were detected. No novel polymorphisms were found in patients with bipolar affective disorder. These polymorphisms were genotyped in a sample of 129 patients and 252 controls of German origin and 176 patients and 182 controls of British origin. No strong associations were found between any of these polymorphisms and bipolar affective disorder. Genetic variation at the 5-HT2A receptor gene does not play a major role in the pathogenesis of the disorder.

Alleles↗

In vivo effects on striatal dopamine D2 receptor binding by the novel atypical antipsychotic drug sertindole--a 123I IBZM single photon emission tomography (SPET) study.

The novel antipsychotic drug sertindole has an atypical pharmacological profile. We have estimated striatal D2 dopamine binding in schizophrenic patients treated with sertindole using 123I iodobenzamide (IBZM) SPET. Patients were recruited from a clinical trial of sertindole's tolerability and efficacy. Striatal D2 binding in sertindole-treated patients (n = 5), was compared with previously reported data from clozapine (n = 10); olanzapine (n = 6); typical antipsychotic responsive (n = 10); and risperidone (n = 6)-treated groups. Mean PANSS (structured clinical interview for the positive and negative syndrome scale) scores showed clinical improvement in the sertindole group. Few extrapyramidal side effects (EPS) were recorded [average Simpson-Angus (SAS) score = 2.6]. Sertindole-treated patients had mean D2 binding indices (+/-SE) significantly lower than clozapine-treated patients (1.19 +/- 0.04) versus (1.49 +/- 0.04), and olanzapine-treated patients (1.41 +/- 0.06); and similar to those of risperidone (1.24 +/- 0.04) and typical antipsychotic responsive (1.25 +/- 0.05) treated patients. In this patient sample the preliminary evidence suggests that sertindole's decreased tendency to induce EPS at clinically therapeutic doses is not due to limited occupancy of striatal D2 receptors in vivo, and as is the case for risperidone, patients are protected from EPS by some other intrinsic effect of the drug.

Adult↗

Nurse-initiated extubation following cardiac surgery.

Early extubation is now advocated for most patients after cardiac surgery. This article contains an examination of changes in extubation practice and addresses the development and implementation of a protocol for nurse-led extubation for this patient group. The knowledge and experience required by nurses to undertake this role is discussed and suggestions for auditing this aspect of nursing care explained.

Cardiac Surgical Procedures↗

Clotting factor IX levels in C/EBP alpha knockout mice.

Previous studies have indicated that C/EBP alpha is involved in the regulation of factor IX and mutations of a C/EBP recognition element in the factor IX promoter result in haemophilia B. We now report that mice homozygous for the deletion of the c/ebp alpha gene are significantly deficient in factor IX transcription.

Animals↗

Effects of octreotide on liver regeneration and tumour growth in the regenerating liver.

The ability of the liver to regenerate following resection is remarkable. However, there is evidence to suggest that tumour growth within the regenerating liver is significantly increased. As octreotide (a synthetic analogue of somatostatin) inhibits the growth and development of hepatic tumour in rats, we have investigated its effects on liver regeneration, liver blood flow, hepatic reticuloendothelial system activity and tumour growth in the rat following partial hepatectomy (PH). Octreotide significantly inhibited liver regeneration in the rat 1 and 2 weeks following PH when compared with controls (regeneration index: 1.0 and 1.14 cf. 1.14 and 1.4, respectively). There was no significant difference in hepatic arterial or portal venous blood flow following PH in control or octreotide-treated rats. However, portal pressure was significantly reduced in octreotide-treated rats. Hepatic reticuloendothelial system activity was significantly increased in octreotide-treated rats compared with control animals 1 and 2 weeks after hepatectomy (uptake of radiolabelled technetium-99m albumin colloid: 2.2 and 3.9 cf. 1.6 and 1.9). The growth of both HSN (fibrosarcoma) and K12-Tr (colonic adenocarcinoma) cells in the regenerating liver was significantly decreased by octreotide treatment compared with controls (median percentage hepatic replacement: HSN control 71.3%, Octreotide 8.4%, K12-Tr Control 38.3%, Octreotide 4.5%). The results of the present study demonstrate that octreotide inhibits both liver regeneration and tumour growth following PH, possibly via a similar mechanism.

Animals↗