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Biomedical subjects

T M O'Brien

Publications and source records attributed to T M O'Brien.

At least 19 recordsLinked to original sources
PubMed2002

Measuring movement at the low back.

The clinical importance of movements of the human spine is increasingly being realized but their measurement is difficult to carry out. Traditionally, measurement of spinal motion focuses on the lumbar spine as the mobile region and movement at the lower thoracic spine is largely ignored. The aim of this study was to test the hypothesis that sagittal movement at the low back is not confined to the lumbar spine. The range of sagittal movement and the amount of skin distraction during trunk flexion was studied in 10 normal subjects. Angular movement in the sagittal plane between the vertebra prominens and S2 ranged between 40 degree and 83 degree among the subjects. Concomitant skin distraction showed that a mean of 32% (range 20-41%) of the movement between the upper thorax and sacropelvis occurred cranial to T12. We therefore suggest that the term "low back" should be applied to a series of mobile vertebrae in the lower thoracic and lumbar spines and that motion of this region in the sagittal plane should be considered as the movement of an immobile upper thoracic spine relative to the sacropelvis.

Adult↗
PubMed2001

The Caulobacter crescentus flagellar gene, fliX, encodes a novel trans-acting factor that couples flagellar assembly to transcription.

The first flagellar assembly checkpoint of Caulobacter crescentus couples assembly of the early class II components of the basal body complex to the expression of class III and IV genes, which encode extracytoplasmic structures of the flagellum. The transcription of class III/IV flagellar genes is activated by the response regulator factor, FlbD. Gain of function mutations in flbD, termed bfa, can bypass the transcriptional requirement for the assembly of class II flagellar structures. Here we show that the class II flagellar gene fliX encodes a trans-acting factor that couples flagellar assembly to FlbD-dependent transcription. We show that the overexpression of fliX can suppress class III/IV gene expression in both wild-type and flbD-bfa cells. Introduction of a bfa allele of flbD into cells possessing a deletion in fliX restores motility indicating that FliX is not a structural component of the flagellum, but rather a trans-acting factor. Furthermore, extragenic motile suppressors which arise in DeltafliX cells map to the flbD locus. These results indicate that FlbD functions downstream of FliX in activating class III/IV transcription. beta-Lactamase fusions to FliX and analysis of cellular fractions demonstrate that FliX is a cytosolic protein that demonstrates some peripheral association with the cytoplasmic membrane. In addition, we have isolated a mutant allele of fliX that exhibits a bfa-like phenotype, restoring flbD-dependent class III/IV transcription in strains that contain mutations in class II flagellar structural genes. Taken together, these results indicated both a positive and negative regulatory function for FliX in coupling the assembly of class II basal body components to gene expression.

Bacterial Proteins↗
PubMed2000

An empirical model for megavoltage x-ray output factors.

An empirical model of the factors that determine the central axis dose at 10 cm depth in water for 4 MV, 6 MV and 18 MV photon beams is presented. Backscattering from the variable collimators into the dose monitoring ionization chamber can cause a variation of -0.5% to +1.8% in the dose per monitor unit in accelerators with an electron facility. Forward emission towards the isocentre from the beam flattening filter and upper collimators is more dependent on the position of the upper variable collimator blades than the lower blades, so that they are not interchangeable in determining output factors, which can differ by up to 2%. The model includes the product of the monitor backscatter factor, normalized phantom scatter factor, normalized head scatter factor and inverse square law, corrected for the displacement of the virtual x-ray focus from the target. It can predict the dose to -/+0.83% for 4 MV, -/+0.80% for 6 MV photons and -/+0.82% for 18 MV photons. The normalized head scatter factor is a second-order polynomial of the modified equivalent square collimator, whose coefficients do not vary significantly with x-ray energy. The model was tested by comparison with independent measurements of output factor and generally agreed to around 1%.

Models, Statistical↗
PubMed2000

The nucleotide sequence of koala (Phascolarctos cinereus) retrovirus: a novel type C endogenous virus related to Gibbon ape leukemia virus.

A novel retrovirus, morphologically consistent with mammalian C-type retroviruses, was detected by electron microscopy in mitogen-stimulated peripheral blood mononuclear cell cultures from 163 koalas and in lymphoma tissue from 3 koalas. PCR amplified provirus from the blood and tissues of 17 wild and captive koalas, and reverse transcriptase-PCR demonstrated viral mRNA, viral genomic RNA, and reverse transcriptase activity in koala serum and cell culture supernatants. Comparison of viral sequences derived from genomic DNA and mRNA showed identity indicative of a single retroviral species-here designated koala retrovirus (KoRV). Southern blot analysis of koala tissue genomic DNA using labelled KoRV probes demonstrated banding consistent with an endogenous retrovirus. Complete and apparently truncated proviruses were detected in DNA of both clinically normal koalas and those with hematopoietic disease. KoRV-related viruses were not detected in other marsupials, and phylogenetic analysis showed that KoRV paradoxically clusters with gibbon ape leukemia virus (GALV). The strong similarity between GALV and KoRV suggests that these viruses are closely related and that recent cross-host transmission has occurred. The complete proviral DNA sequence of KoRV is reported.

Animals↗
PubMed1998

Quantitative analysis and classification of gait patterns in cerebral palsy using a three-dimensional motion analyzer.

Gait disorders in cerebral palsy can be accurately analyzed using the CODA-3 system presenting quantitative data representing movement of the hip, knee, and ankle in the sagittal plane. We describe a technique that classifies abnormal gait automatically on the basis of sagittal kinematic data. Fifty-five hemiplegic and 91 diplegic patients were analyzed using an opto-electronic scanner (CODA-3). The sagittal kinematics of the affected limb in hemiplegics correlated with those of both affected limbs in diplegics. We introduce the concept of the "plegic limb." Sagittal kinematics of 237 affected limbs were studied using cluster statistical analysis. Eight clear groups emerged. The predominant clinical features, typical of each group, were identified and described (eg, stiff leg gait, genu recurvatum, or crouch gait). We propose this classification system as a new technique to use gait analysis data to automatically classify abnormal movements of the lower limb in cerebral palsy.

Adolescent↗
PubMed1997

The effect of tourniquet release time on the analgesic efficacy of intraarticular morphine after arthroscopic knee surgery.

A randomized, controlled study was conducted in patients undergoing elective arthroscopic knee surgery to assess the effects of tourniquet release time on analgesia after intraarticular (I.A.) injection of morphine. Standardized general anesthetic and surgical techniques were used for all patients, including a thigh tourniquet inflated at pressures between 300 and 350 mm Hg. At the conclusion of the arthroscopic procedure, 5 mg morphine in 25 mL saline was administered I.A. Patients were then randomized to one of two treatment groups. In Group 1 (n = 20), the tourniquet was kept inflated for 10 min after I.A. injection, whereas in Group 2 (n = 20), the tourniquet was deflated immediately after I.A. injection. Postoperative pain was assessed using a visual analog scale in the recovery room when the patients were awake and at 2, 4, 6, 8, and 24 h after I.A. injection. Patients who complained of pain in the recovery room received increments of intravenous meperidine 25-50 mg. On discharge from the recovery room, patients received oral mefenamic acid 250-500 mg for pain relief. The time and quantity of analgesics required were recorded. Patients in Group 1 had significantly (P < 0.05) lower pain scores than those in Group 2 at 2, 4, 6, and 8 h postoperatively. These low pain scores were associated with lower requirements of supplementary analgesics. We conclude that, as compared with releasing the tourniquet immediately after I.A. injection of morphine, maintaining the tourniquet inflated for 10 min provides superior analgesia and decreases the need for supplemental analgesics.

Adult↗
PubMed1996

The bicycle spoke injury: an avoidable accident?

A prospective study of the bicycle spoke injury over a 1-year period included a total of 71 spoke injuries. Of these, 67 injuries occurred on an adult bicycle and four occurred on a child's bicycle. All children sustained ankle and foot injuries, which consisted of contusion and superficial abrasion (N = 45), skin loss (N = 10), skin laceration (N = 4), and undisplaced fractures (N = 12). A biomechanical study was conducted to investigate the use of a protective cover over the wheel to prevent the foot from slipping between the spokes. Wind resistance studies showed that a cover with a mesh size of 10 mm hexagonal could prevent this and at the same time stop the cover from acting as a sail if a flat cover without holes was used instead. The mesh cover, however, will prevent the toes from entering between the spokes but will not prevent the foot from becoming jammed between the wheel and the fork. To prevent this, a plastic shield to bridge the gap between the fork and the horizontal upright has been designed. With these modifications, the bicycle spoke injury can become an injury of the past.

Adolescent↗
PubMed1995

Intra-articular analgesia for arthroscopic meniscectomy.

Intra-articular morphine has been shown to provide prolonged analgesia after arthroscopic knee surgery; the addition of local anaesthetic agents has been reported to improve this analgesic effect. Pethidine possesses local anaesthetic properties, and therefore this study was designed to evaluate its analgesic efficacy after arthroscopic meniscectomy. Sixty patients were allocated randomly to receive intra-articular injections of pethidine 50 mg, morphine 5 mg or saline after elective arthroscopic meniscectomy. Postoperative pain was assessed using an interval visual analogue scale and measuring analgesic requirements. Both treatment groups had significantly lower pain scores compared with the control group. Patients in the pethidine group had lower pain scores than those in the morphine group at 0.5, 1 and 2 h, but significantly higher scores at 12 and 24 h. These observations suggest that the local anaesthetic effect of pethidine may be responsible for the improved early analgesia, but its duration of action appears to be less than that of morphine.

Adolescent↗
PubMed1993

Intraarticular analgesia following knee arthroscopy.

A randomized, double-blind, controlled study was conducted in patients undergoing elective knee arthroscopy to assess the analgesic effect of intraarticular morphine and bupivacaine, alone and in combination. Patients in group 1 (n = 10) received 5 mg of morphine in 25 mL of saline; patients in group 2 (n = 10) received 25 mL of 0.25% bupivacaine (62.5 mg); patients in group 3 (n = 10) received a combination of 5 mg of morphine and 62.5 mg of bupivacaine in 25 mL dilution; and patients in group 4 (n = 10) received 25 mL of saline. All the drugs were injected intraarticularly. Postoperative pain was assessed using the visual analogue scale at 1, 2, 4, 8, and 24 h after the intraarticular injection. The need for supplemental analgesia was recorded. Results showed that there was no significant difference in the pain scores or analgesic requirements between groups 1 and 3. Patients in groups 1 and 3 had significantly lower pain scores than those in groups 2 and 4. These low pain scores were associated with lower requirements of supplementary analgesics. The patients in group 4 showed the highest pain scores and analgesic requirements. We conclude that intraarticular morphine significantly reduces postoperative pain following knee arthroscopy and that there is no advantage of combining bupivacaine with morphine.

Adult↗
PubMed1992

Intra-articular morphine for pain relief after knee arthroscopy.

We performed a randomised double-blind controlled study in patients undergoing elective knee arthroscopy to assess the effect of intra-articular morphine on postoperative pain relief. Patients in the study group (n = 10) received 5 mg of morphine in a 25 ml dilution intra-articularly while those in the control group (n = 10) received 25 ml of saline. Postoperative pain was assessed at intervals by a visual analogue scale and the requirement for supplementary analgesia was recorded. Those in the study group had significantly lower pain scores and required less systemic analgesics than those in the control group. Plasma profiles for morphine and its metabolites were assayed and showed that they were too low to produce effective analgesia. Evidence suggests that analgesia was mediated by local action within the joint.

Anesthesia Recovery Period↗
PubMed1990

Movement of the femoral head after Salter osteotomy for acetabular dysplasia.

A Salter innominate osteotomy is used to treat acetabular dysplasia, but reports of its effects on the position of the femoral head are few and conflicting. Lateral shift would increase the resultant forces acting on the joint and be detrimental. We studied 15 Salter innominate osteotomies and demonstrated that a correctly performed osteotomy does not significantly alter the distance from the centre of the femoral head to the midline of the body. Stereophotogrammetry was used in three patients to delineate the axis of rotation of the distal acetabular fragment and determine the locus of movement of the centre of the femoral head about it. Our results explain why the Salter osteotomy does not lateralise the femoral head.

Acetabulum↗
PubMed1989

The aetiology of degenerative disease of the hip. A review of 400 cases.

Four-hundred and forty patients who presented for Total Hip Replacement to the Orthopaedic Hospital, Cappagh were included in this study. Each case was classified into radiographic and aetiologic groups on the basis of the patients history, the results of special investigations, and the radiographic appearance of the hips. This classification allowed a further differentiation into primary and secondary osteoarthritis. Primary or idiopathic osteoarthritis was the single most common aetiologic group. A surprisingly high percentage of patients with secondary osteoarthritis had congenital dysplasia. It is suggested that this faulty biomechanical situation is the initiator of subsequent joint degeneration due to stress loading on the supero-lateral border of the hip. The reasons why such changes may be delayed until the 6th and 7th decades are unclear but degeneration once started progresses quickly. The possible place of surgical correction of the underlying biomechanical fault in delaying or preventing the onset of osteoarthritis is demonstrated and discussed.

Hip Prosthesis↗
PubMed1989

Osteoarthritis of the hip and Heberden's nodes.

One hundred consecutive patients with proved osteoarthritis were assessed for the presence of terminal interphalangeal joint disease. There was a significant association found between the presence of Heberden's nodes and primary (axillary) arthritis. Secondary osteoarthritis was relatively free of nodal involvement. It is suggested that Heberden's nodes are a helpful clinical marker in differentiating between the two major groups of osteoarthritis.

Female↗
PubMed1988

Bilateral stress fractures of the ulna.

A previously undescribed case of bilateral stress fractures of the ulna is reported. The cause is attributed to inappropriate use of weight-bearing crutches. Biomechanical comparison is made with other known causes of stress fractures in the bones of the upper limb.

Adolescent↗
PubMed1987

Femoral anteversion. A clinical assessment of idiopathic intoeing gait in children.

Hip rotation in extension and flexion was studied in 23 patients with idiopathic intoeing gait. In extension all the hips had markedly increased medial rotation and limited lateral rotation, fulfilling the criteria of excessive femoral anteversion. In flexion, however, rotation varied widely; in one group of patients medial rotation remained greater than lateral, but in the second group lateral rotation was equal to or greater than medial. CT scans showed that the hips in the first group were significantly more anteverted than those in the second. Clearly measurement of hip rotation in extension alone does not provide a dependable indication of femoral anteversion in children with intoeing gait; rotation in flexion also needs to be measured.

Child↗