Search PubMed⌕ Search

Biomedical subjects

A J Martin

Publications and source records attributed to A J Martin.

At least 19 recordsLinked to original sources
PubMed2005

High-resolution characterization of the canine DLA-DRB1 locus using reference strand-mediated conformational analysis.

Several methods exist for genotyping class II DLA gene polymorphisms in the dog. The most accurate method is sequence-based typing, which involves direct sequencing of polymerase chain reaction products. However, this method is expensive and unsuitable for large-scale studies. Recently, reference strand-mediated conformation analysis (RSCA) has been shown to be effective for characterizing major histocompatibility complex genes in humans, sheep, horse, and cats. RSCA is a cheap and rapid method, ideal for large epidemiological studies. We have developed RSCA for typing DLA-DRB1 in the dog. Control panels including dogs typed by sequence-based typing and cloned major histocompatibility complex class II alleles in plasmids were used to establish migration patterns for each allele using 20 different fluorescent labeled references, of which 5 were selected to allow for clear identification and discrimination of all known DLA-DRB1 alleles. We have compared 168 dogs typed by RSCA for DLA-DRB1 and characterized by sequence-based typing, with less than 1% discrepancy. These differences were due to missing alleles because of a weak polymerase chain reaction. To date, we have RSCA-typed 1,394 dogs. RSCA is likely to become the method of choice for characterizing DLA genes in the dog and will prove a useful tool for dissecting the immune response of dogs in clinical studies.

Alleles↗
PubMed2005

The assessment of an intermittent high intensity running test.

AIM: In multiple sprint sports the ability to perform repeated short duration bouts of maximal intensity exercise appears to be sport specific than the ability to perform prolonged continuous exercise or produce a single bout of exercise. However, previous studies have not verified a field test method with an appropriate intermittent anaerobic exercise pattern. The purpose of this study was to establish the reliability and validity of the Intermittent Anaerobic Running Test (IAnRT) primarily developed for soccer players. METHODS: Twenty-nine trained male adolescent soccer players performed two separate 20 m sprints and the IAnRT on an indoor running track in each of two testing sessions separated by one recovery day. The IAnRT consisted of 10 20-m sprints with 20-s recovery periods between the sprints. RESULTS: The mean running speed (Vm) and the speed at the beginning and the end of the IAnRT (V1+2, V9+10) confirmed good reliability. The relative mean speed index was the preferred indicator for assessing the ability to maintain short duration running performance during the intermittent exercise mode. Using confirmatory factor analysis the running performance of IAnRT was best explained by one general factor and one subfactor which consequently joined the general one from the 6th sprint (P=0.03, Bentler's d=0.99, RMSR=0.03). CONCLUSION: The IAnRT provided reliable and valid performance indices, which reflect the maximal anaerobic running power and capacity for repeated running sprints.

Adolescent↗
PubMed2004

Reduced neurocognition in children who snore.

Obstructive sleep apnea syndrome (OSAS) has been associated with reduced neurocognitive performance in children, but the underlying etiology is unclear. The aim of this study was to evaluate the relationship between hypoxemia, respiratory arousals, and neurocognitive performance in snoring children referred for adenotonsillectomy. Thirteen snoring children who were referred for evaluation regarding the need for adenotonsillectomy to a children's hospital otolaryngology/respiratory department underwent detailed neurocognitive and polysomnographic (PSG) evaluation. PSGs were evaluated for respiratory abnormalities and compared with 13 nonsnoring control children of similar age who were studied in the same manner. The snoring children had an obstructive respiratory disturbance index within normal range (mean obstructive apnea/hypopnea index, 0.6/hr). Despite this, several domains of neurocognitive function were reduced in the snoring group. These included mean verbal IQ scores (snorers 92.6 vs. nonsnorers 110.2, P < 0.001), mean global IQ scores (snorers 96.7 vs. nonsnorers 110.2, P < 0.005), mean selective attention scores (snorers 46.4 vs. nonsnorers 11.8, P < 0.001), mean sustained attention scores (snorers 8.0 vs. nonsnorers 2.2, P = 0.001), and mean memory index (snorers 95.2 vs. nonsnorers 112.1, P = 0.001). There was a direct relationship between number of mild oxygen desaturations of > or = 3%, obstructive hypopneas with > or = 3% oxygen desaturations, and respiratory arousals and severity of neurocognitive deficits, with the greatest effect being on memory scores. The disruption of sleep in snoring children produced by relatively mild changes in oxygen saturation or by increases in respiratory arousals may have a greater effect on neurocognitive function than hitherto appreciated. A possible explanation for these neurocognitive deficits may be the combination of the chronicity of sleep disruption secondary to snoring which is occurring at a time of rapid neurological development in the first decade of life. Future studies need to confirm the reversal of these relatively mild neurocognitive decrements post adenotonsillectomy.

Analysis of Variance↗
PubMed2003

Measurement and analysis of brain deformation during neurosurgery.

Recent studies have shown that the surface of the brain is deformed by up to 20 mm after the skull is opened during neurosurgery, which could lead to substantial error in commercial image-guided surgery systems. We quantitatively analyze the intraoperative brain deformation of 24 subjects to investigate whether simple rules can describe or predict the deformation. Interventional magnetic resonance images acquired at the start and end of the procedure are registered nonrigidly to obtain deformation values throughout the brain. Deformation patterns are investigated quantitatively with respect to the location and magnitude of deformation, and to the distribution and principal direction of the displacements. We also measure the volume change of the lateral ventricles by manual segmentation. Our study indicates that brain shift occurs predominantly in the hemisphere ipsi-lateral to the craniotomy, and that there is more brain deformation during resection procedures than during biopsy or functional procedures. However, the brain deformation patterns are extremely complex in this group of subjects. This paper quantitatively demonstrates that brain deformation occurs not only at the surface, but also in deeper brain structure, and that the principal direction of displacement does not always correspond with the direction of gravity. Therefore, simple computational algorithms that utilize limited intraoperative information (e.g., brain surface shift) will not always accurately predict brain deformation at the lesion.

Adult↗
PubMed2002

Neurocytoma of the thoracic spinal cord.

Central neurocytoma is an unusual tumour that arises in the supratentorial ventricular system of young adults. Similar lesions, termed simply neurocytoma, have been described at a variety of locations outside the ventricular system. Here, we report the case of a 50-year-old man who presented with pain and a rapidly progressive myelopathy due to a neurocytoma of the upper thoracic spinal cord. The literature on spinal neurocytoma and its relation to central neurocytoma are discussed.

Disease Progression↗
PubMed2001

Biopsy needle tip artifact in MR-guided neurosurgery.

A thorough understanding of both the appearance and origin of metallic biopsy needle tip artifact in magnetic resonance imaging (MRI) as well as its interaction with various magnetic resonance (MR) sequence parameters is beneficial for its application in today's MR-guided therapeutic procedures. In a more practical setting, this investigation has focused on the characteristics of MR image artifacts associated with a finite-length metallic needle, specifically at the tip of a biopsy needle when it is approximately parallel to the main magnetic field. The image artifact at needle tip, which exhibits as a blooming ball-shaped signal void, was demonstrated and studied using MR imaging and numerical simulation employing the finite difference method (FDM). In order to understand the origin of this image artifact, a numerical model or simulation software based on the FDM has been developed specifically to solve for the field disturbance to a uniform magnetic field due to a finite-length metallic needle. The solution for magnetic field shows that the field disturbance is spatially localized at the needle tip. From the numerical results, simulated images were generated which were in a very satisfactory agreement MR imaging experiment. Results showed that the MR image artifacts associated with MR-compatible metallic biopsy needles are not only present due to the magnetic susceptibility difference between the needle and its surrounding tissue, but also predictable in routine MR-guided procedures, and the size of the image artifacts could be reduced if optimal imaging parameters were used. J. Magn. Reson. Imaging 2001;13:16-22.

Artifacts↗
PubMed2001

An efficient chemical shift imaging scheme for magnetic resonance-guided neurosurgery.

An efficient magnetic resonance spectroscopic imaging (MRSI) or chemical shift imaging (CSI) technique based on multiple spin echoes (MSE) has been implemented, validated, and used in both phantom and in vivo MR-guided neurosurgical applications. The key concept of the method is to employ MSE to significantly speed up the data collection rate for mapping hydrogen-containing metabolites. Using an echo train length (ETL) of three per excitation to simultaneously fill three consecutive k-space areas, the total scan time for a spectroscopic image matrix size of 32 x 32 has been shortened to approximately 11 minutes. An interecho spacing time of 273 msec was used to null the phase anomalies of lactate double peaks due to the J-coupling. This allowed a sufficient long data sampling time to achieve 4 Hz spectral resolution. Performing CSI intraopertively during an MR-guided neurosurgical procedure was shown to be feasible at 1.5 T. More importantly, it was shown that more relevant information can be obtained regarding neurochemistry about a targeted lesion, in addition to conventional MR morphological imaging noninvasively. In 25 MR-guided neurosurgical cases, the alleviated choline signal has been found to be consistent with the existence of rapid tumor cell proliferation in the corresponding area. The actual neurobiopsy guided by the spectroscopic imaging method demonstrated that it could provide valuable information in specifying the optimal site in a biopsy procedure, especially in the case involving a nonenhancing tumor. The multiecho scheme has made the CSI technique efficient enough to be routinely used in MR-guided surgical procedures at 1.5 T and also allows the possibility of taking full advantage of MRI capability.

Adult↗
PubMed2001

Efficacy of once-daily tobramycin monotherapy for acute pulmonary exacerbations of cystic fibrosis: a preliminary study.

Our objective was to compare the efficacy, safety, and microbiology of once-daily intravenous (IV) tobramycin with conventional 8-hourly tobramycin/ceftazidime IV therapy for acute Pseudomonas aeruginosa (PA) pulmonary exacerbations in cystic fibrosis (CF). CF patients with PA-induced pulmonary exacerbations were allocated to receive either once-daily tobramycin (Mono) or conventional therapy with tobramycin/ceftazidime given 8-hourly (Conv). The two longitudinal groups received therapy in a double-blind, randomized manner over a period of 2 years. Tobramycin doses were adjusted to achieve a daily area under the time-concentration curve of 100 mg x hr/L in both groups. Results were assessed for both short-term changes (efficacy and safety after 10 days of IV antibiotics during acute exacerbations) and long-term changes (efficacy, safety, and sputum microbiology between study entry and exit). Pulmonary function tests (PFTs) on admission were similar in both groups. After 10 days of IV antibiotics, absolute mean improvements in percent of predicted PFTs were 12.8, 12.1, and 13.7 for forced expiratory volume in 1 sec (FEV(1)), forced vital capacity (FVC), and forced expired flow between 25--75% of FVC (FEF(25--75%)) in the Conv group (n = 51 admissions) compared to 10.6, 9.9, and 10.6 in the Mono group (n = 47)(P<0.05 for all). Sixteen percent in the Conv group and 15% of patients in the Mono group did not respond to therapy by day 10. Long-term PFT patterns were similar for the Conv and Mono groups. The time between admissions did not differ. The Mono group showed a significant increase in tobramycin minimum inhibitory concentrations (MICs) against PA from study entry to study exit (P = 0.02, n = 27 strains); this failed to reach significance in the Conv group (P = 0.08, n = 25). There was no significant increase in the number of isolates, with MIC> or =8 mg/L in both groups. No short- or long-term changes in audiology or serum creatinine were found in either group. After 10 days of IV therapy, the urinary enzyme N-acetyl-beta-d-glucosaminidase/creatinine ratios increased in both groups (P0.05). This increase was greater in the Conv compared to the Mono group (P < 0.05). We conclude that this pilot study indicates once-daily tobramycin therapy to be as effective and safe as conventional 8-hourly tobramycin/ceftazidime therapy. Combination antibacterial therapy appears to offer no clinical advantage over once-daily tobramycin monotherapy. Tobramycin once-daily monotherapy is a potential alternative to conventional IV antibacterial therapy which deserves further investigation, including the impact on susceptibility of PA to tobramycin.

Adolescent↗
PubMed2001

The strange association of pneumosinus dilatans and arachnoid cyst: case report and review of the literature.

BACKGROUND: The authors present the case of a 71-year-old man with dramatic pneumosinus dilatans adjacent to a large, symptomatic, fronto-temporal arachnoid cyst. METHOD: The literature on pneumosinus dilatans and its association with arachnoid cyst is reviewed. FINDINGS: Pneumosinus dilatans may be either idiopathic, a reaction to an adjacent meningioma, or an 'ex-vacuo' response to cerebral volume loss and intracranial hypotension. It is also found with large arachnoid cysts and is probably under-recognised in this context. The co-existence of an expansile intradural lesion with changes in the skull base that tend to reduce the intracranial volume is puzzling, and has not yet been fully explained. Differences in the relative timing of paranasal sinus and arachnoid cyst growth, and the 'temporal agenesis' theory of arachnoid cyst formation have been proposed but do not account for all the features of this unusual association. INTERPRETATION: Pneumosinus dilatans is a useful and under-recognised indicator of the presence and chronicity of a variety of intracranial pathologies. Its association with arachnoid cyst is paradoxical, and a new explanation is offered as to how this may arise.

Aged↗
PubMed2001

Acute respiratory infection in patients with cystic fibrosis with mild pulmonary impairment: comparison of two physiotherapy regimens.

Chest physiotherapy is an essential part of the management of cystic fibrosis, yet comparatively few studies have investigated the commonly used forms of chest physiotherapy during acute respiratory exacerbations. Fifteen subjects with cystic fibrosis and predominantly mild pulmonary impairment completed a randomised cross-over trial with 24 hours between treatments. The active cycle of breathing techniques (ACBT) assisted by a physiotherapist was compared with the ACBT performed independently by the patient. Measurement outcomes included pulmonary function tests, indirect calorimetry and oximetry parameters. Energy expenditure was not significantly different between the two treatment regimens, though significant improvements in pulmonary function were apparent 24 hours following the therapist-assisted ACBT. In this group of subjects, neither form of treatment proved superior in terms of energy consumption, but a reduction in airways obstruction was observed as a carry-over effect following the therapist-assisted ACBT.

Acute Disease↗
PubMed2001

Solitary fibrous tumours of the meninges: case series and literature review.

We report four new cases of meningeal Solitary Fibrous Tumour (SFT). Two patients presented with raised intracranial pressure from posterior fossa SFT, and the third developed hemiparesis and dysphasia due to a large lesion that originated in the left middle cranial fossa. These were successfully excised and the patients remain well at follow-up of between 1 and 3 years. The fourth patient, a 71-year-old man, suffered an intracerebral haemorrhage and later died from a malignant SFT that had invaded the falx cerebri, superior sagittal sinus, and brain. This is the first description of a locally aggressive meningeal SFT with multiple atypical histological features. The 31 previously reported cases of meningeal SFT are reviewed. They occur at all ages and may be relatively more common in the posterior fossa and spine. Intracranial SFT originate from the dura and are probably indistinguishable from meningiomas on imaging and at surgery. In contrast, approximately two-thirds of spinal SFT have no dural attachment. Histologically, SFT are spindle-cell neoplasms with a characteristic immunohistochemical profile of CD34, vimentin, and bcl-2 positivity. Data on outcome for patients with meningeal SFT are limited. At other sites, however, extent of resection is the most important prognostic factor, and invasion or metastasis can occur with histologically benign SFT. Meningeal SFT should, therefore, be excised as completely as possible and followed carefully in the long-term.

Adult↗
PubMed2001

Ultrastructural examination is essential for diagnosis of papillary meningioma.

AIMS: Papillary meningioma is a rare meningeal tumour. To date only a few cases have been reported and their immunohistochemical features have not been fully documented. METHODS AND RESULTS: A 49-year-old woman presented with a 2-month history of headaches and memory disturbance. CT and MRI imaging showed an enhancing pineal mass with extension into the occipital lobes and invasion of the splenium. At surgery, the tumour was found to be tough and vascular with a well-defined capsule. No recurrence was noted 19 months after the operation. In another case a 44-year-old woman was admitted with 1-month history of headaches, poor memory, imbalance and diplopia. CT scan showed a large hyperdense, uniformly, enhancing mass within the middle cranial fossa at the petrous ridge. The tumour recurred 19 and 25 months after first resection. The histology of both tumours was similar. The neoplasms contained polygonal cells with a moderate amount of cytoplasm, rounded regular nuclei and distinct cell borders. The cells were arranged radially around the blood vessels (perivascular pattern) and a papillary pattern was seen only focally. Mitotic figures were moderately frequent. Immunohistochemistry showed that both tumours were immunoreactive to vimentin and NSE, whereas GFAP, CAM5.2, EMA, S100 protein and synaptophysin were negative. Electron microscopy revealed interdigitating cell processes, desmosomes and intermediate filaments. CONCLUSIONS: The histological and immunohistochemical features of these two tumours are complex and difficult to interpret. Although papillary meningiomas were considered in our initial differential diagnosis, the final conclusion was possible only when the ultrastructural features were revealed.

Biopsy↗