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Biomedical subjects

B Irwin

Publications and source records attributed to B Irwin.

At least 19 recordsLinked to original sources
PubMed2006

Levetiracetam in pregnancy: preliminary experience from the UK Epilepsy and Pregnancy Register.

It is not known whether the antiepileptic drug (AED) levetiracetam can be used safely in human pregnancy. As part of a study to determine the risks of major congenital malformations (MCMs) for infants exposed to AEDs in utero, we identified all cases exposed to levetiracetam. Three of 117 exposed pregnancies had an MCM (2.7%; 95% CI 0.9% to 7.7%); all 3 were exposed to other AEDs.

Abnormalities, Drug-Induced↗
PubMed2005

Malformation risks of antiepileptic drugs in pregnancy: a prospective study from the UK Epilepsy and Pregnancy Register.

OBJECTIVE: To assess the relative risk of major congenital malformation (MCM) from in utero exposure to antiepileptic drug (AEDs). METHODS: Prospective data collected by the UK Epilepsy and Pregnancy Register were analysed. The presence of MCMs recorded within the first three months of life was the main outcome measure. RESULTS: Full outcome data were collected on 3607 cases. The overall MCM rate for all AED exposed cases was 4.2% (95% confidence interval (CI), 3.6% to 5.0%). The MCM rate was higher for polytherapy (6.0%) (n = 770) than for monotherapy (3.7%) (n = 2598) (crude odds ratio (OR) = 1.63 (p = 0.010), adjusted OR = 1.83 (p = 0.002)). The MCM rate for women with epilepsy who had not taken AEDs during pregnancy (n = 239) was 3.5% (1.8% to 6.8%). The MCM rate was greater for pregnancies exposed only to valproate (6.2% (95% CI, 4.6% to 8.2%) than only to carbamazepine (2.2% (1.4% to 3.4%) (OR = 2.78 (p<0.001); adjusted OR = 2.97 (p<0.001)). There were fewer MCMs for pregnancies exposed only to lamotrigine than only to valproate. A positive dose response for MCMs was found for lamotrigine (p = 0.006). Polytherapy combinations containing valproate carried a higher risk of MCM than combinations not containing valproate (OR = 2.49 (1.31 to 4.70)). CONCLUSIONS: Only 4.2% of live births to women with epilepsy had an MCM. The MCM rate for polytherapy exposure was greater than for monotherapy exposure. Polytherapy regimens containing valproate had significantly more MCMs than those not containing valproate. For monotherapy exposures, carbamazepine was associated with the lowest risk of MCM.

Anticonvulsants↗
PubMed2001

Clinical outcomes that fetal surgery for myelomeningocele needs to achieve.

INTRODUCTION: The development of techniques to close open neural tube malformations prior to birth has generated great interest and hope for fetal interventions and their outcomes. To plan a randomized trial, as is being discussed at three centres in the United States, the determination of what constitutes a clinically significant improvement in outcome is critical. To date, preliminary observations from two centres suggest that improvements may occur, not in spinal cord function as originally postulated, but in the extent of the hindbrain hernia and the frequency that shunting is required to control hydrocephalus. PURPOSE: The determination of what outcome would constitute an important and clinically significant difference in outcome to be achieved by fetal intervention for myelomeningocele. METHOD: Parents of patients and patients treated in our myelomeningocele clinic were surveyed using a structured and validated tool. From the perspective of a recommendation to a close friend or family member, the interviewees were asked to quantify on a scale from 0 to 100 the chance of specific outcomes (need for a shunt, need for a wheelchair, change of urinary incontinence) that a fetal operation would need to predictably achieve. RESULTS: Responses were obtained from 77 patients/families. The fifty percentile response in each study dimension was as follows: the chance of needing a shunt was 12 % (range 0 - 50 %), the chance of needing a wheelchair was 8 % and the chance of being incontinent was 5 % (range 0 - 25 %). CONCLUSIONS: Fetal interventions will have to achieve significant improvements in the control of hydrocephalus, mobilization and continence over postnatal treatment to be justified.

Adult↗
PubMed1996

Assessment of the appropriateness of services provided by a multidisciplinary meningomyelocele clinic.

Since 1969, the Meningomyelocele Clinic at British Columbia's Children's Hospital has been serving the needs of children with spina bifida. In 1994, the clinic provided urgent and routine multidisciplinary clinical assessments to 330 patients and families. The purpose of this study was to assess, from the patients' and families' perspective, the appropriateness of the frequency of routine clinic visits and the value of the health services provided. Sixty-five patients/families were interviewed and completed a questionnaire developed by the clinic. Current visit frequency and services provided appear to meet the patient/family needs. The medical and nursing contributions were seen as valuable resources for the patient/families resulting in most patient/families feeling well informed about spina bifida.

Child↗
PubMed1995

Codon pair utilization biases influence translational elongation step times.

Two independent assays capable of measuring the relative in vivo translational step times across a selected codon pair in a growing polypeptide in the bacterium Escherichia coli have been employed to demonstrate that codon pairs observed in protein coding sequences more frequently than predicted (over-represented codon pairs) are translated slower than pairs observed less frequently than expected (under-represented codon pairs). These results are consistent with the findings that translational step times are influenced by codon context and that these context effects are related to the compatabilities of adjacent tRNA isoacceptor molecules on the surface of a translating ribosome. These results also support our previous suggestion that the frequency of one codon next to another has co-evolved with the structure and abundance of tRNA isoacceptors in order to control the rates of translational step times without imposing additional constraints on amino acid sequences or protein structures.

Amino Acid Sequence↗
PubMed1994

Autoregulation of hip, an operon that affects lethality due to inhibition of peptidoglycan or DNA synthesis.

The hip locus of Escherichia coli affects the frequency of persistence to the lethal consequences of selective inhibition of either DNA or peptidoglycan synthesis. Regulation of the hip operon, which consists of a regulatory region and two genes, hipB and hipA, was examined with strains containing a hip-lac transcriptional fusion placed in single copy at the lambda att site. Disruption of the hip locus increased activity from the fusion 16-fold. Repression was restored by supplying HipB in trans. HipB was overexpressed and purified. On the basis of gel filtration and cross-linking studies, HipB is a dimer in solution. Sequence analysis revealed that HipB is a Cro-like DNA-binding protein. The interaction of HipB with the hip regulatory region was examined by gel retardation, DNase I protection, and methylation protection studies. HipB binds with a Kapp (K apparent) of 40 pM to four operator sites with the conserved sequence TATCCN8GGATA (N represents any nucleotide). Binding to the operators is nearly simultaneous and appears to be cooperative. Analysis of the role of HipA in the regulation of the hip operon is complicated by the toxicity of HipA in the absence of HipB. Strains disrupted in hipB but not in hipA could not be recovered. Moreover, hipA-containing plasmids cannot be replicated in strains defective in or lacking hipB. HipA is found exclusively in a tight complex with HipB. Although disruption of hipA slightly increased expression from the hip-lac fusion, in vitro studies suggest that HipA does not bind to the hip regulatory region directly but indirectly via HipB.

Bacterial Proteins↗
PubMed1992

The bowel management tube: an effective means for controlling fecal incontinence.

Regular bowel washout enemas have been used as a method of management of fecal incontinence. The effective administration of a washout enema to a child with weak anal sphincters is often a problem. Using a new silastic balloon-tipped enema catheter (bowel management tube [BMT]) of our design, we prospectively studied its effectiveness in a group of children who suffered fecal incontinence. Thirty-one children were studied over a 1-year period. Their diagnoses included meningomyelocele (19), postoperative Hirschsprung's disease or imperforate anus (10), and other (2). Before and after starting the BMT enema system, clinical assessment and a diary, which graded the degree of fecal incontinence and satisfaction with the system, were completed. Five patients failed to benefit because of noncompliance (3) or balloon extrusion (2). Three more patients discontinued the use of the tube system. Twenty-three patients achieved successful results with this system as evidenced by a significant amelioration in their fecal incontinence and their unwillingness to give up the use of the BMT. We conclude that the use of a regular washout enemas with BMT can be an effective method for control of fecal incontinence in children.

Adolescent↗
PubMed1990

Acute and subacute hematologic effects of multi-colony stimulating factor in combination with granulocyte colony-stimulating factor in vivo.

Multi-colony stimulating factor (Multi-CSF, interleukin-3, IL-3) and granulocyte-CSF (G-CSF) administered concurrently as an intravenous (IV) injection induce a peripheral neutrophilia that is approximately additive in comparison with the neutrophilia induced by IL-3 and G-CSF individually. The bone marrow (BM) at 12 hours is depleted of mature neutrophils and shows a left-shifted myeloid hyperplasia, consistent with the neutrophil-releasing and myeloproliferative activities of both IL-3 and G-CSF individually. The BM at 24 hours shows a replenished reserve of mature neutrophils and a synergistic left-shifted myeloid hyperplasia as compared with IL-3 and G-CSF alone. Daily IV injections of IL-3 plus G-CSF for 1 week also induce an approximately additive daily peripheral neutrophilia. The BM after a week's administration of IL-3 plus G-CSF shows a generalized myeloid hyperplasia with a synergistic increase in mature neutrophils as compared with IL-3 or G-CSF alone. Daily injection of IL-3 plus G-CSF induced a significant decrease in erythroid, lymphoid, and eosinophilic marrow precursors, possibly owing to a myelophthisic effect of the myeloid hyperplasia and despite the fact that IL-3 alone induced a significant erythroid hyperplasia.

Animals↗
PubMed1990

Endotoxin-induced cytokine gene expression in vivo. II. Regulation of tumor necrosis factor and interleukin-1 alpha/beta expression and suppression.

Tumor necrosis factor alpha (TNF alpha) mRNA is present in a preformed intracellular pool in the spleen, liver, and small bowel of naive rats. Endotoxin (Salmonella typhus lipopolysaccharide) injected intravenously induces little or no increase in whole-organ TNF mRNA levels at 15', 30', 1 degree, 2 degrees, or 4 degrees, whereas serum TNF levels are markedly elevated at 1 and 2 hours. Dexamethasone pretreatment of rats suppresses LPS-induced serum TNF concentrations, but does not suppress TNF mRNA levels in the spleen or bowel. Tachyphylaxis experiments demonstrate that a second injection of endotoxin 2 hours after an initial injection fails to induce a second peak of serum TNF, although TNF mRNA levels in the spleen and bowel remain at the levels found in naive rats. Corynebacterium parvum upregulates endotoxin-induced serum TNF release and intravenous injection of IL-1 induces the release of serum TNF but neither alters whole-organ TNF mRNA levels. Interleukin-1 alpha (IL-1 alpha) mRNA was not constitutively detected in whole-organ RNA preparations of the spleen, liver, and small bowel of naive rats. Endotoxin induces IL-1 alpha mRNA most easily appreciated in the spleen beginning at 1 hour, peaking at 2 to 4 hours, and disappearing by 6 hours. Interleukin-1 beta (IL-1 beta) mRNA was not constitutively detected in the organs examined or was present in small amounts. Endotoxin induces IL-1 beta mRNA beginning at 0.5 hours, peaking at 1 hour, and disappearing by 6 hours. Dexamethasone pretreatment prevents the LPS-induced appearance of IL-1 alpha mRNA and suppresses but does not completely inhibit the appearance of IL-1 beta mRNA. C. parvum upregulates endotoxin-induced IL-1 mRNA expression. Intravenous injection of TNF or IL-1 both induce IL-1 mRNA expression. In conclusion, TNF mRNA is constitutively expressed and TNF mRNA levels as analyzed in whole-organ RNA preparations do not change in concert with serum TNF protein levels during conditions of endotoxemia, dexamethasone treatment, tachyphylaxis, priming with C. parvum, or after injection of IL-1. In contrast, IL-1 mRNA expression during endotoxemia, dexamethasone treatment, priming with C. parvum, or after injection of TNF or IL-1 shows clear increases and decreases in whole-organ RNA preparations.

Animals↗
PubMed1988

Incidence and morbidity of cytomegalovirus disease associated with a seronegative recipient receiving seropositive donor-specific transfusion and living-related donor transplantation. A multicenter evaluation.

This retrospective study was conducted to identify the frequency of cytomegalovirus (CMV) disease in seronegative recipients of donor-specific transfusion (DST) and living-related donor (LRD) kidneys from seropositive donors. A total of 151 LRD transplants (TX) were performed at six transplant centers over a 3-year period. A total of 33 patients were identified as having been seronegative (pre-TX) for CMV, yet they had DST and a TX from a seropositive LRD. Of these patients, 12 (36.4%) seroconverted within the first 6 months post-TX and developed clinical CMV disease. Additional patients seroconverted, but did not have evidence of clinical disease and were not tested further. All TX centers, with the exception of one, had seronegative patients that became ill after receiving a seropositive DST/LRD TX. Six patients manifested their disease as a febrile illness with leukopenia and liver enzyme elevations, four had pneumonitis, and two developed CMV ulcerations of the colon (one of whom died from resultant sepsis). Of the 36 seronegative patients who received seronegative DST/LRD TX none became ill with CMV disease. Of the 72 seropositive patients who received DST/LRD TX, only 2 (2.8%) developed CMV illness (one, seropositive into seropositive, the other, seronegative into seropositive). Of the 33 seronegative patients receiving seropositive DST/LRD TX, 17 received antilymphocyte preparations (ALP), and 8 of these became ill (47.1%). Of 16 patients not receiving ALP, 5 (31.3%) developed clinical CMV illness. Of the 33 patients who were identified as having been seronegative for CMV yet received seropositive DST/LRD TX, the 12 who did develop CMV illness had two graft losses, one death, and a serum creatinine for the remaining 9 patients of 2.3 +/- 1.6 at last follow-up. The remaining 21 patients who developed no illness had a serum creatinine of 1.3 +/- 0.6 with no graft losses at the last follow-up. This evidence suggests that a prospective TX recipient who is seronegative for CMV who receives DST/LRD TX from a seropositive family member has a significant risk for developing morbidity related to clinical CMV illness.

Adolescent↗
PubMed1987

Reversal of progressive renal allograft dysfunction with OKT3.

The safety and efficacy of treatment with Orthoclone OKT3 was evaluated in 14 renal transplant patients with allograft dysfunction unresponsive to conventional therapy. Eleven of the 14 initially improved on OKT3, and 9 have retained their kidneys after a median 13-month follow-up. The mean serum creatinine among successes is 2.4 mg/dl. It is concluded that OKT3 is a safe and effective drug for treatment of rejection, and may be used during temporary discontinuation of ciclosporin in cases in which nephrotoxicity is questioned.

Antibodies, Monoclonal↗
PubMed1977

Exercise performance in 6-to-11-year-old boys with Duchenne muscular dystrophy.

To determine effects of severe muscular dystrophy on the performance of dynamic exercise, cardiorespiratory responses to incremental work on a bicycle ergometer and isokinetic limb strength measurements were compared for 13 dystrophic boys and 13 normal, untrained boys. The dystrophic boys (D) were matched to the normal boys (N) on the basis of age (8.4 yr), height (125 cm) and weight (25.7 kg). At rest, the dystrophic group had higher heart rates (HR) (D = 102; D = 31; N = 39 ml), with no difference in oxygen uptake (VO2), calculated cardiac output (Q), pulmonary ventilation (VE), or respiratory exchange ratio (R). During submaximal work, VO2, SV, Q and VE were lower in D. During maximal work, D had lower peak values for work rate (D = 400; N = 600 kg/min), endurance (D = 41; N = 60 ml), Q (D = 5.2; N = 11.0 liters/min), VE (D = 8.2; N = 36.9 liters/min), and R (D = 0.84; N = 0.99). Arm and leg strengths (four flexion and four extension motions) were lower in D, but muscle girths were not necessarily smaller. The findings indicate exercise performance in D was below normal and limited by low cardiorespiratory capacities, diminished leg strength, and perhaps reduced peripheral oxygen utilization. Duchenne muscular dystrophy, even in its early stages, apparently affects the work capacity of cardiac and pulmonary muscles as well as limb muscles.

Anthropometry↗
PubMedDate not supplied

Prenatal spinal evaluation and functional outcome of patients born with myelomeningocele: information for improved prenatal counselling and outcome prediction.

OBJECTIVE: Prenatal ultrasonography can localize the level of the spinal cord malformation, allowing prediction of the potential postnatal neurological deficit and functional prognosis. METHODS: This study has two evaluations: (a) a retrospective prenatal review of 26 fetuses with spinal dysraphism (1987-1991), and (b) a follow-up descriptive study of patients (1971-1981) who underwent closure of the spinal lesion and ventricular shunting in the neonatal period. RESULTS: Prenatal ultrasound evaluation enabled the accurate definition of the last intact vertebral level which allows separation of fetuses into three functional groups (last intact level L2, L3-4, L5-sacral). Patterns of ambulation, urinary and bowel continence, and school performance vary according to level of spinal lesion and the neurological deficit. The need for ventricular shunts, the incidence of other spinal malformations and surgical interventions did not vary with the level of the spinal lesion. CONCLUSIONS: The functional outcome for patients with myelomeningocele is variable; however, distinct patterns emerge based on the level of spinal dysraphism and the resultant neurological deficit. By relating the level of the fetal spinal lesion to outcome data, more precise functional prognoses can be given to families.

Counseling↗