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Biomedical subjects

J Brennan

Publications and source records attributed to J Brennan.

At least 19 recordsLinked to original sources
PubMed2005

Endovascular repair of abdominal aortic aneurysms with aortocaval fistula.

OBJECTIVES: To examine the risk of high-flow type II endoleak following endovascular repair of abdominal aortic aneurysm with aortocaval fistula. DESIGN: Case reports. SUBJECTS: Two patients with abdominal aortic aneurysms with aortocaval fistula. METHODS: Both patients had an endovascular repair of their aortic aneurysms. RESULTS: The aneurysms were successfully treated in both patients, without any endoleak on completion angiography. Apart from a transient type II lumbar endoleak in one of the patients, no endoleak was found after 3 and 12 month follow-up. Seven other cases have been published, reporting one type II and one type Ic endoleak. CONCLUSION: We found no evidence that endovascular repair of abdominal aortic aneurysm with aortocaval fistula is associated with a higher incidence of persistent endoleak.

Aged↗
PubMed2004

Syringomyelia with Chiari malformation; 3 unusual cases with implications for pathogenesis.

Syringomyelia is an important cause of neurological deficit. Most cases of non-traumatic syringomyelia occur in association with a Chiari malformation. We present three unusual examples of syringomyelia with such an association. The first case is that of syringomyelia in a young woman with Marfan's syndrome, a spontaneous CSF leak and intractable intracranial hypotension. The second is a woman with long-standing lumbo-peritoneal shunt for pseudotumour cerebri who developed an acquired Chiari malformation. A young woman with a Dandy-Walker cyst that herniated into the upper cervical canal is the third case. These cases provide a basis for discussion of the pathogenesis and management of syringomyelia and the Chiari malformation in such cases.

Adult↗
PubMed2004

The mouse frizzled 8 receptor is expressed in anterior organizer tissues.

Wnt signaling has been shown to be important for axis formation in vertebrates. However, no Wnt ligand or receptor has been shown to be specifically expressed in all the organizer tissues in the mouse embryo. Here we report that the mouse frizzled 8 (mfz8) gene, a Wnt receptor, is expressed in the anterior visceral endoderm (AVE) and the anterior primitive streak, which have been shown to possess organizer activity. mFz8 is also expressed in the descendents of the anterior streak that comprise the anterior mesendoderm (AME) at midgastrulation, with subsequent expression in the anterior neurectoderm, which is specified and patterned by the AVE and AME. Thus, mfz8 is specifically expressed in the organizer tissues that establish the anterior-posterior axis in the mouse embryo.

Animals↗
PubMed2003

A disturbance of nonlinear interdependence in scalp EEG of subjects with first episode schizophrenia.

It has been proposed that schizophrenia arises through a disturbance of coupling between large-scale cortical systems. This "disconnection hypothesis" is tested by applying a measure of dynamical interdependence to scalp EEG data. EEG data were collected from 40 subjects with a first episode of schizophrenia and 40 matched healthy controls. An algorithm for the detection of dynamical interdependence was applied to six pairs of bipolar electrodes in each subject. The topographic organization of the interdependence was calculated and served as the principle measure of cortical integration. The rate of occurrence of dynamical interdependence did not statistically differ between subject groups at any of the sites. However, the topography across the scalp was significantly different between the two groups. Specifically, nonlinear interdependence tended to occur in larger concurrent "clusters" across the scalp in schizophrenia than in the healthy subjects. This disturbance was reflected most strongly in left intrahemispheric coupling and did not differ significantly according to symptomatology. Medication dose and subject arousal were not observed to be confounding factors. The study of dynamical interdependence in scalp EEG data does not support a straightforward interpretation of the disconnection hypothesis-that there is a decrease in the strength of functional coupling between adjacent cortical regions. Rather, it suggests a dysregulation in the organization of dynamical interactions across supraregional brain systems.

Adolescent↗
PubMed2003

The efficacy of bacitracin methylene disalicylate when fed in combination with narasin in the management of necrotic enteritis in broiler chickens.

The efficacy of bacitracin methylene disalicylate (BMD) in the management of necrotic enteritis (NE) when fed in combination with narasin was investigated in a floor-pen study of 2,000 broiler chickens using a Clostridium perfringens inoculum challenge model. Treatments consisted of 1) nonchallenged-nonmedicated; 2) challenged-nonmedicated; 3) challenged-narasin (70 ppm); 4) challenged-BMD (55 ppm); 5) challenged-narasin (70 ppm) + BMD (55 ppm). Medication was provided in the feed from Day 0 to trial termination on Day 41. C. perfringens challenge occurred from Day 14 to 16. BMD and narasin, fed alone and in combination, reduced (P < 0.05) mortality due to NE when compared to challenged-nonmedicated birds. NE lesion scores (Days 0 through 41) were lower among birds fed BMD and narasin, alone and in combination, compared to challenged-nonmedicated birds. Improvements in NE mortality and NE lesion scores were greatest for the BMD + narasin-medicated birds, followed by the BMD-alone, and then narasin-alone treated birds. BMD and narasin, alone and in combination, provided improvements (P < 0.05) in average daily gains over the entire study (Days 0 to 41). The results of this study demonstrate the effectiveness of BMD and narasin in the management of NE in broiler chickens.

Animals↗
PubMed2002

An introduction to digital radiography in dentistry.

The aim of this article is to explain the basic principles of digital radiography, and to discuss the intra- and extra-oral imaging systems currently available. There are two main types of digital sensors available. One is based on charge coupled device technology and the other consists of phosphor storage plates. The advantages and disadvantages of each are highlighted with particular attention to orthodontics.

Cephalometry↗
PubMed2002

Experimental evaluation of flow patterns in interposition vein cuff anastomosis. The influence of non-planarity of the inflow.

Clinical evidence suggests that the development of myointimal hyperplasia in prosthetic femorodistal bypass grafts may be reduced by the interposition of a cuff of autologous vein between the graft and the recipient artery. Previous experimental work has shown that some of the benefits may be attributed to the geometry of the cuffed anastomosis. Since the distal anastomosis in vivo is often non-planar we have carried out a preliminary study in a model where the graft is at an angle of 45 degrees to the anterior-posterior plane of the anastomosis. This out-of-plane angulation produces highly asymmetric flow patterns in the anastomosis with significant flow separation on the ipsilateral side of the cuff. In the proximal and distal outflow, however, the velocity vectors show significant helical motion with temporal instability in the distal outflow.

Anastomosis, Surgical↗
PubMed2002

Community and social interventions at a geriatric medical OPD.

Health and social services in Ireland tend to be relatively poorly coordinated. Surveys confirm the perceptions of older people with disability that access to and availability of both health and social services are limited. Multi-disciplinary geriatric medical clinics may provide a focus for better utilization and coordination of these services. The purpose of this study was to measure not only the existing service use but also the potential for community and social-care intervention with older people living in the community when using multi-disciplinary geriatric medical clinics. A sample of 60 consecutive patients aged over 65, attending our geriatric medical OPD for the first time, were interviewed using a semistructured questionnaire on the current and potential use of community and social care services. Our service arranged for 229 interventions or referral to services, an average of 3.8 interventions per patient. Ninety-six services were already in place (an average of 1.6 per patient) and 455 services were not applicable, an average of 7.6 per patient. A combined health and social care response is critical to a successful strategy to disease and disability in later life. Although this study describes a relative utilitarian approach to increase community and social care support, it shows there is significant scope to improve uptake of basic community and social care services by a focussed approach to the care needs of older people.

Aged↗
PubMed2001

Identification and characterisation of a developmentally regulated mammalian gene that utilises -1 programmed ribosomal frameshifting.

Translational recoding of mRNA through a -1 ribosomal slippage mechanism has been observed in RNA viruses and retrotransposons of both eukaryotes and prokaryotes. Whilst this provides a potentially powerful mechanism of gene regulation, the utilization of -1 translational frameshifting in regulating mammalian gene expression has remained obscure. Here we report a mammalian gene, Edr, which provides the first example of -1 translational recoding in a eukaryotic cellular gene. In addition to bearing functional frameshift elements that mediate expression of distinct polypeptides, Edr bears both CCHC zinc-finger and putative aspartyl protease catalytic site retroviral-like motifs, indicative of a relic retroviral-like origin for Edr. These features, coupled with conservation of Edr as a single copy gene in mouse and man and striking spatio-temporal regulation of expression during embryogenesis, suggest that Edr plays a functionally important role in mammalian development.

Amino Acid Motifs↗
PubMed2001

Nodal signalling in the epiblast patterns the early mouse embryo.

Shortly after implantation the mouse embryo comprises three tissue layers. The founder tissue of the embryo proper, the epiblast, forms a radially symmetric cup of epithelial cells that grows in close apposition to the extra-embryonic ectoderm and the visceral endoderm. This simple cylindrical structure exhibits a distinct molecular pattern along its proximal-distal axis. The anterior-posterior axis of the embryo is positioned later by coordinated cell movements that rotate the pre-existing proximal-distal axis. The transforming growth factor-beta family member Nodal is known to be required for formation of the anterior-posterior axis. Here we show that signals from the epiblast are responsible for the initiation of proximal-distal polarity. Nodal acts to promote posterior cell fates in the epiblast and to maintain molecular pattern in the adjacent extra-embryonic ectoderm. Both of these functions are independent of Smad2. Moreover, Nodal signals from the epiblast also pattern the visceral endoderm by activating the Smad2-dependent pathway required for specification of anterior identity in overlying epiblast cells. Our experiments show that proximal-distal and subsequent anterior-posterior polarity of the pregastrulation embryo result from reciprocal cell-cell interactions between the epiblast and the two extra-embryonic tissues.

Animals↗
PubMed2001

Magnesium sulfate in the treatment of refractory ventricular fibrillation in the prehospital setting.

OBJECTIVE: To determine if magnesium sulfate (MgSO(4)) improves outcome in cardiac arrest patients initially in ventricular fibrillation (VF). METHODS: Randomized, prospective, double blind, placebo-controlled, multicenter prehospital trial using 2 g of MgSO(4). Eligible patients were non-traumatic cardiac arrest patients (> or =18 years of age) presenting in VF. The protocol included those patients refractory to three electroshocks. Epinephrine and either 2 g of MgSO(4) or placebo (normal saline) were then administered. The primary outcome variable was return of spontaneous circulation (ROSC) in the field and a perfusing pulse on arrival at the ED. Secondary endpoints included admission to the hospital (ADMT) and hospital discharge (DISC). IRB approval was obtained at all participating centers. RESULTS: Total 116 patients (58 MgSO(4), 58 placebo) were enrolled during the period from 4/1992 to 10/96 with 109 available. There were no significant differences between the groups in baseline characteristics and times to cardio pulmonary resuscitation (CPR), advanced life support (ALS), and first defibrillation, except for time to study drug administration. There was no significant differences in ROSC (placebo, 18.5%, and MgSO(4), 25.5%, P=0.38), ADMT (placebo rate=16.7%, MgSO(4)=16.4%, P=1.0) or DISC (placebo rate=3.7%, MgSO(4)=3.6%, P=1.0). CONCLUSIONS: We failed to demonstrate that the administration of 2 g of MgSO(4) to prehospital cardiac arrest patients presenting in VF improves short or long term survival.

Adolescent↗
PubMed2001

From fertilization to gastrulation: axis formation in the mouse embryo.

Although much remains unknown about how the embryonic axis is laid down in the mouse, it is now clear that reciprocal interactions between the extraembryonic and embryonic lineages establish and reinforce patterning of the embryo. At early post-implantation stages, the extraembryonic ectoderm appears to impart proximal-posterior identity to the adjacent proximal epiblast, whereas the distal visceral endoderm signals to the underlying epiblast to restrict posterior identity as it moves anteriorward. At gastrulation, the visceral endoderm is necessary for specifying anterior primitive streak derivatives, which, in turn, pattern the anterior epiblast. Polarity of these extraembryonic tissues can be traced back to the blastocyst stage, where asymmetry has been linked to the point of sperm entry at fertilization.

Animals↗
PubMed2001

Aortic side branch embolization before endovascular aneurysm repair: incidence of type II endoleak.

PURPOSE: To assess the feasibility of embolization of aortic side branches and its impact on the incidence of type II endoleak after endovascular aneurysm repair. MATERIALS AND METHODS: Endovascular aneurysm repair was performed in 74 patients. Aortic side branch vessels were evaluated on the preoperative angiogram and computed tomography (CT) and, where embolization of lumbar and inferior mesenteric vessels was considered technically possible, this was attempted prior to endovascular repair. Follow-up CT was used to assess the presence of type II endoleak. RESULTS: Seventy-two patients were followed up for longer than 1 month. Embolization was attempted in 25 cases, successfully in 10, with partial success in 11, and failure in four. Twenty patients with successful or partly successful preoperative embolization were discharged and followed-up. Four (20%) had demonstrable type II endoleak during follow-up, with two of these persisting at latest follow-up. Of 43 patients without previous embolization, there were 10 (23.3%) type II endoleaks during the follow-up period, four of these persisting. In cases with type II endoleak, mean sac diameter change was -0.5 mm in the cases with previous embolization and +3.1 mm without. The mean period to onset of type II endoleak was 6.9 months without, and 15.3 months with, previous embolization. CONCLUSION: Although the cohort size is below a level that would confer significance, the trend of these findings is such as to suggest a lack of influence of aortic side branch embolization on the incidence of type II endoleak during the follow-up period.

Angiography↗
PubMed2001

Functional analysis of secreted and transmembrane proteins critical to mouse development.

We describe the successful application of a modified gene-trap approach, the secretory trap, to systematically analyze the functions in vivo of large numbers of genes encoding secreted and membrane proteins. Secretory-trap insertions in embryonic stem cells can be transmitted to the germ line of mice with high efficiency and effectively mutate the target gene. Of 60 insertions analyzed in mice, one-third cause recessive lethal phenotypes affecting various stages of embryonic and postnatal development. Thus, secretory-trap mutagenesis can be used for a genome-wide functional analysis of cell signaling pathways that are critical for normal mammalian development and physiology.

Animals↗
PubMed2001

Prospective analysis of the efficacy of continuous intraoperative nerve monitoring during thyroidectomy, parathyroidectomy, and parotidectomy.

OBJECTIVE: Continuous intraoperative electromyographic monitoring was prospectively performed in all parotidectomies, thyroidectomies, and parathyroidectomies over approximately 5 years to assess the efficacy of this technology. STUDY DESIGN AND SETTING: Continuous intraoperative nerve monitoring with perioperative nerve assessment was performed. The postresection minimal stimulation level of the nerves was determined to evaluate if this level would predict nerve function postoperatively. RESULTS: Forty-four parotidectomies and 70 thyroid/parathyroid operations were performed with 140 nerves at risk (44 facial, 96 recurrent laryngeal). The incidence of temporary facial paralysis was 15.9% (7 of 44) and the incidence of permanent paralysis was 0%. The incidence of temporary recurrent laryngeal nerve paralysis in terms of nerves at risk was 1.0% (1 of 96), and the incidence of permanent recurrent laryngeal nerve paralysis was 0%. All patients with normally functioning facial and recurrent laryngeal nerves postoperatively had minimal stimulation levels less than or equal to 0.4 mA. CONCLUSION: Continuous intraoperative nerve monitoring was associated with extremely low rates of temporary and permanent nerve paralysis in our series of 140 nerves at risk as compared to the rates documented in the literature.

Adolescent↗
PubMed2001

Mitochondrial function and oxygen supply in normal and in chronically ischemic muscle: a combined 31P magnetic resonance spectroscopy and near infrared spectroscopy study in vivo.

PURPOSE: We used (31)P magnetic resonance spectroscopy (MRS) and near-infrared spectroscopy (NIRS) as a means of quantifying abnormalities in calf muscle oxygenation and adenosine triphosphate (ATP) turnover in peripheral vascular disease (PVD). METHODS: Eleven male patients with PVD (mean age, 65 years; range, 55-76 years) and nine male control subjects of similar age were observed in a case-control study in vascular outpatients. Inclusion criteria were more than 6 months' calf claudication (median, 1.5 years; range, 0.6-18 years); proven femoropopliteal or iliofemoral occlusive or stenotic disease; maximum treadmill walking distance (2 km/h, 10 degrees gradient) of 50 to 230 m (mean, 112 m); ankle-brachial pressure index of 0.8 or less during exercise (mean, 0.47; range, 0.29-0.60). Exclusion criteria included diabetes mellitus, anemia, and magnet contraindications. Simultaneous (31)P MRS and NIRS of lateral gastrocnemius was conducted during 2 to 4 minutes of voluntary 0.5 Hz isometric plantarflexion at 50% and 75% maximum voluntary contraction force (MVC), followed by 5 minutes recovery. Each subject was studied three times, and the results were combined. RESULTS: Compared with control subjects, patients with PVD showed (1) normal muscle cross-sectional area, MVC, ATP turnover, and contractile efficiency (ATP turnover per force/area); (2) larger phosphocreatine (PCr) changes during exercise (ie, increased shortfall of oxidative ATP synthesis) and slower PCr recovery (47% +/- 7% [mean +/- SEM] decrease in functional capacity for oxidative ATP synthesis, P = .001); (3) faster deoxygenation during exercise and slower postexercise reoxygenation (59% +/- 7% decrease in rate constant, P = .0009), despite reduced oxidative ATP synthesis; (4) correlation between PCr and NIRS recovery rate constants (P < .02); and (5) correlations between smaller walking distance, slower PCr recovery, and reduced MVC (P < .001). The precision of the key measurements (rate constants and contractile efficiency) was 12% to 18% interstudy and 30% to 40% intersubject. CONCLUSION: The primary lesion in oxygen supply dominates muscle metabolism. Reduced force-generation in patients who are affected more may protect muscle from metabolic stress.

Adenosine Triphosphate↗
PubMed2001

Efficacy of in-feed tylosin phosphate for the treatment of necrotic enteritis in broiler chickens.

The efficacy of tylosin phosphate for the treatment of necrotic enteritis (NE) was investigated in a floor pen study of 2,000 broiler chickens. A model in which Clostridium perfringens was administered in the feed on Days 14 to 16 was used to initiate an outbreak of NE. Treatments, allocated at the pen level in a randomized complete block design, consisted of five levels of tylosin phosphate (0, 50, 100, 200, or 300 ppm) administered in the feed on Days 15 to 22, following the identification of an outbreak of NE on Day 15. Mortality due to NE was significantly reduced (P < 0.05) for medicated birds at all dose levels of tylosin phosphate compared to unmedicated birds. Mean NE lesion scores on Day 17 were significantly reduced (P < 0.05) by all levels of tylosin treatment compared to those of unmedicated birds, decreasing linearly from 2.66 at 0 ppm to 0.38 at 100 ppm and 0 at higher doses. Tylosin at all levels provided improvement in Day 29 body weight, average daily gain, feed to gain ratio, and average daily feed intake compared to unmedicated birds. The results of this study provide evidence that tylosin phosphate, when administered in feed, is effective in the treatment of clinical outbreaks of NE in broiler chickens and suggest that the optimal dose for this purpose is 100 ppm.

Animal Feed↗