Auxin receptors: a new role for F-box proteins

The plant hormone auxin regulates transcription by promoting the degradation of a family of transcriptional repressors called Aux/IAA proteins. Genetic and biochemical studies have shown that this degradation is dependent on a ubiquitin protein ligase called SCF(TIR1). In the presence of auxin, the F-box protein TIR1 binds to the Aux/IAA proteins, resulting in their ubiquitination and degradation. Recent attention has focused on the nature of the auxin receptor and upstream signaling events involved in this process. Now, two recent papers demonstrate that auxin binds directly to TIR1 and promotes the interaction with the Aux/IAA proteins. Furthermore, TIR1 functions together with at least three other related F-box protein/receptors to mediate the auxin response throughout plant growth and development.

Regulation of cullin-based ubiquitin ligases by the Nedd8/RUB ubiquitin-like proteins

The expression of the ubiquitin related protein Nedd8/RUB is essential for growth in most organisms. Nedd8/RUB has been shown to modify the cullin subunit of culling-based ubiquitin protein ligases (E3). Neddylation acts to regulate the function of these E3s and organisms with lesions in the neddylation process exhibit severe growth defects. In this review we describe the proteins that participate in neddylation and discuss a model for Nedd8/RUB regulation of ubiquitin ligase function.

Post-transplant lymphoproliferative disorders presenting as gingival overgrowth in patients immunosuppressed with ciclosporin. A report of two cases

BACKGROUND

Post-transplant lymphoproliferative disorder (PTLD) can occur in patients maintained on immunosuppressive therapy following transplantation. This paper describes two cases of PTLD occurring in gingival tissues, in patients receiving ciclosporin following cardiac transplantation.

TREATMENT

The lesions were localised to gingival tissues, mimicking ciclosporin-induced gingival overgrowth. They were removed surgically and the ciclosporin dose reduced to help prevent recurrence.

CONCLUSION

The importance of histopathological examination of all tissue removed during routine gingivectomy procedures for ciclosporin-induced gingival overgrowth is highlighted.

The stethoscope: some preliminary investigations

Textbooks, clinicians, and medical teachers differ as to whether the stethoscope bell or diaphragm should be used for auscultating respiratory sounds at the chest wall. Logic and our results suggest that stethoscope diaphragms are more appropriate.

The stethoscope: some preliminary investigations

Textbooks, clinicians, and medical teachers differ as to whether the stethoscope bell or diaphragm should be used for auscultating respiratory sounds at the chest wall. Logic and our results suggest that stethoscope diaphragms are more appropriate.

Is midwife workload associated with quality of process of care (continuous electronic fetal monitoring [CEFM]) and neonatal outcome indicators? A prospective study in consultant-led labour wards in Scotland

Evidence for staffing recommendations in labour wards is scant. This study aimed to test association between midwife workload with adjusted process of continuous electronic fetal monitoring (CEFM) and neonatal outcome indicators. This was a prospective workload study in 23 consultant-led labour wards in Scotland. There were 3489 livebirths during September 2000, and 1561 consecutively delivered women with CEFM case review during the mid-two weeks. Process measures were: adjusted rates of CEFM, appropriate CEFM, and time to medical response for a serious fetal heart trace abnormality. Neonatal outcome indicators were: Apgar score < 7 at 5 minutes, admission to neonatal unit (NNU) > 48 hours, and neonatal resuscitation. Complete information was available for 99% (2553/2576) of workload time points, 99% (1559) of CEFM process, and 3083 eligible neonates. There were no associations between occupancy or staffing ratios and adjusted CEFM process, Apgar < 7 at 5 minutes (0.98 [0.83, 1.15]) or admission to NNU for > 48 hours (0.97 [0.95, 1.00]). However, there was association between increasing staffing ratios and lower odds of adjusted neonatal resuscitation (excluding bag and mask only) (0.97 [0.94, 0.99]). The direction of effect of increasing workload suggests detriment to outcome indicators, although the size of effect may be small.

Pediatric cardiac transplant: results using a steroid-free maintenance regimen

We report on survival, rejection, lymphoma and renal function following cardiac transplant using a steroid-free maintenance immunosuppressive regimen. We have performed 73 cardiac transplants in 71 children under 16 yr of age in the last 12 yr. There were eight perioperative and four late deaths giving actuarial survival of 88, 88, 85 and 70% at 1, 2, 5 and 10 yr, respectively. A total of 11 (15.3%) children had one episode of rejection (grade 3) in the first 6 months; one died and one was re-transplanted because of rejection. There was only one episode of late rejection (8 yr post-transplant) because of low drug levels in a patient with lymphoma and sepsis. This patient did not survive. Three other children (5.6%) also developed lymphoma and recovered but one died subsequently of graft failure. Four children have developed severe renal failure (glomerular filtration rate GFR <30 mL/min/m2). Two have not survived and one is expected to commence dialysis soon. The remainder have mild to moderate renal impairment. We report excellent survival and low rejection rates without use of long-term steroids. However the doses of cyclosporin used have had a significant effect on renal function in many cases.

Tissue factor deficiency causes cardiac fibrosis and left ventricular dysfunction

Exposure of blood to tissue factor (TF) activates the extrinsic (TF:FVIIa) and intrinsic (FVIIIa:FIXa) pathways of coagulation. In this study, we found that mice expressing low levels of human TF ( approximately 1% of wild-type levels) in an mTF(-/-) background had significantly shorter lifespans than wild-type mice, in part, because of spontaneous fatal hemorrhages. All low-TF mice exhibited a selective heart defect that consisted of hemosiderin deposition and fibrosis. Direct intracardiac measurement demonstrated a 30% reduction (P < 0.001) in left ventricular function in 8-month-old low-TF mice compared with age-matched wild-type mice. Mice expressing low levels of murine FVII ( approximately 1% of wild-type levels) exhibited a similar pattern of hemosiderin deposition and fibrosis in their hearts. In contrast, FIX(-/-) mice, a model of hemophilia B, had normal hearts. Cardiac fibrosis in low-TF and low-FVII mice appears to be caused by hemorrhage from cardiac vessels due to impaired hemostasis. We propose that TF expression by cardiac myocytes provides a secondary hemostatic barrier to protect the heart from hemorrhage.

Auxin cross-talk: integration of signalling pathways to control plant development

Plants sense and respond to endogenous signals and environmental cues to ensure optimal growth and development. Plant cells must integrate the myriad transduction events into a comprehensive network of signalling pathways and responses. The phytohormone auxin occupies a central place within this transduction network, frequently acting in conjunction with other signals, to co-ordinately regulate cellular processes such as division, elongation and differentiation. As a non-cell autonomous signal, auxin also interacts with other signalling pathways to regulate inter-cellular developmental processes. As part of this especially themed edition of Plant Molecular Biology, we will review examples of 'cross-talk' between auxin and other signalling pathways. Given the current state of knowledge, we have deliberately focused our efforts reviewing auxin interactions with other phytohormone and light signalling pathways. We conclude by discussing how new genomic approaches and the Arabidopsis genome sequence are likely to impact this area of research in the future.

Auxin cross-talk: integration of signalling pathways to control plant development

Plants sense and respond to endogenous signals and environmental cues to ensure optimal growth and development. Plant cells must integrate the myriad transduction events into a comprehensive network of signalling pathways and responses. The phytohormone auxin occupies a central place within this transduction network, frequently acting in conjunction with other signals, to co-ordinately regulate cellular processes such as division, elongation and differentiation. As a non-cell autonomous signal, auxin also interacts with other signalling pathways to regulate inter-cellular developmental processes. As part of this especially themed edition of Plant Molecular Biology, we will review examples of 'cross-talk' between auxin and other signalling pathways. Given the current state of knowledge, we have deliberately focused our efforts reviewing auxin interactions with other phytohormone and light signalling pathways. We conclude by discussing how new genomic approaches and the Arabidopsis genome sequence are likely to impact this area of research in the future.