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Radiological evaluation before and after treatment with an osseointegrated bone-anchor following major limb amputation-a guide for radiologists. Skeletal Radiol 2024; 53:1033-1043. [PMID: 38044373 PMCID: PMC11001742 DOI: 10.1007/s00256-023-04524-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Revised: 11/19/2023] [Accepted: 11/20/2023] [Indexed: 12/05/2023]
Abstract
Osseointegrated implants have been developed to allow direct skeletal fixation of a prosthesis as an alternative to traditional socket-fitted prostheses for patients who have suffered from a major limb amputation. The implants contribute to improvements in functional outcome and quality of life and radiological evaluation plays a crucial role in pre- and post-operative assessment. This article acts as a guide for radiologists who may be tasked with providing the radiological information required by surgeons and prosthetists. We also look at the radiological appearances of complications that may arise in patients treated with an osseointegrated implant. Plain X-rays are used to screen patients who wish to undergo treatment. Limb-length X-rays are then used to measure the length of any residual bone, and comparisons can be made with the normal side (if present). From this, decisions about the likely size of the implant and the need for further amputation can be made. CT scans enable accurate assessment of the medullary cavity and cortical thickness. Post-operatively, plain X-rays form the mainstay of the routine monitoring of the bone-implant interface. Potential complications include infection, aseptic loosening, mechanical fracture of the implant and periprosthetic fracture. Infection and aseptic loosening can be seen as a lucency at the bone-implant interface which (if left untreated) can lead to loss of the implant. Implant and periprosthetic fractures are radiographically obvious. Radiologists involved in the care of patients undergoing treatment with an osseointegrated implant should become familiar with the imaging requirements so they can contribute to optimal patient outcomes.
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Stable Cortical Body Maps Before and After Arm Amputation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.13.571314. [PMID: 38168448 PMCID: PMC10760201 DOI: 10.1101/2023.12.13.571314] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Neuroscientists have long debated the adult brain's capacity to reorganize itself in response to injury. A driving model for studying plasticity has been limb amputation. For decades, it was believed that amputation triggers large-scale reorganization of cortical body resources. However, these studies have relied on cross-sectional observations post-amputation, without directly tracking neural changes. Here, we longitudinally followed adult patients with planned arm amputations and measured hand and face representations, before and after amputation. By interrogating the representational structure elicited from movements of the hand (pre-amputation) and phantom hand (post-amputation), we demonstrate that hand representation is unaltered. Further, we observed no evidence for lower face (lip) reorganization into the deprived hand region. Collectively, our findings provide direct and decisive evidence that amputation does not trigger large-scale cortical reorganization.
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Quantitative and qualitative analysis of individual experiences post botulinum toxin injection - United Kingdom Survey. SKIN HEALTH AND DISEASE 2023; 3:e265. [PMID: 37799369 PMCID: PMC10549845 DOI: 10.1002/ski2.265] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/30/2023] [Revised: 05/29/2023] [Accepted: 06/13/2023] [Indexed: 10/07/2023]
Abstract
Introduction In the United Kingdom (UK), complications that arise following the administration of Botulinum Toxin are reported to the Medicines and Health Regulatory Agency (MHRA) via the Yellow Card Reporting Scheme. Over the past decade, there has been a significant increase in the number of non-surgical aesthetic procedures. Concerns have been raised that the MHRA is not fully capturing complications in terms of volume and impact on patients. Aim This novel study explores the lived experiences of individuals who have experienced an adverse event following administration of Botulinum Toxin for aesthetic purposes. Using a combination of qualitative and quantitative methodologies, this analysis evaluates data relating to long-lasting physical, psychological, emotional, and financial sequelae of complications arising from cosmetic Botulinum Toxin injections in the UK. Methods A mixed method, qualitative and quantitative approach was adopted to gain comprehensive insights into patients' experiences. A focus group which comprised patient representatives, psychologists, and researchers reached a consensus on a 17-question survey which was disseminated via social media channels. Deductive thematic analysis was used to analyse coded themes. Furthermore, for secondary analysis, sentiment analysis was used computationally as an innovative approach to identify and categorise free text responses associated with sentiments using natural language processing (NLP). Results In the study, 655 responses were received, with 287 (44%) of respondents completing all questions. The mean age of respondents was 42.6 years old. 94.1% of respondents identified as female. In the sample, 79% of respondents reported an adverse event following their procedure, with the most common event being reported as 'anxiety'. Findings revealed that 69% of respondents reported long-lasting adverse effects. From the responses, 68.4% reported not having recovered physically, 63.5% of respondents stated that they had not recovered emotionally from complications, and 61.7% said that they have not recovered psychologically. In addition, 84% of respondents stated that they do not know who regulates the aesthetics industry. Furthermore, 92% of participants reported that their clinic or practitioner did not inform them about the Yellow Card Reporting Scheme. The sentiment analysis using the AFINN Lexicon yielded adjusted scores ranging from -3 to +2, with a mean value of -1.58. Conclusion This is the largest survey in the UK completed by patients who experienced an adverse outcome following the aesthetic administration of Botulinum Toxin. Our study highlights the extent of the challenges faced by patients who experience an adverse event from physical, emotional, psychological, and financial perspectives. The lack of awareness of MHRA reporting structures and the lack of regulation within the UK's cosmetic injectables sector represent a significant public health challenge.
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Cosmetic business mechanics in London: A cross-sectional analysis and audit of ASA compliance. J Cosmet Dermatol 2023; 22:2520-2527. [PMID: 37017936 DOI: 10.1111/jocd.15750] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Accepted: 03/17/2023] [Indexed: 04/06/2023]
Abstract
INTRODUCTION The proliferation of providers and practitioners of cosmetic botulinum toxin and dermal filler has profound public health implications. The Advertising Standards Authority (ASA) regulates the use of advertising materials in the United Kingdom and prohibits the promotion of prescription-only medicines. AIMS We aim to perform a cross-sectional analysis of the practitioners in London, UK to evaluate the distribution of clinics within Greater London, prices advertised for interventions, and compliance with the ASA code. We also aim to identify whether there are any differences in cost of botulinum toxin or dermal filler between the boroughs. METHODS Between December 2021 and January 2022, we performed a systematic search using the internet search engine Google. Five searches were performed (1) [london] botox, (2) [london] botulinum toxin, (3) [london] anti wrinkle injection, (4) [london] filler, (5) [london] dermal filler. One hundred websites per search string were systematically reviewed and those which met the inclusion/exclusion criteria of each search string were included and analyzed. Each clinic's product/service range compliance with the ASA/CAP code was assessed. Any reference to Botulinum Toxin or anti-wrinkle injections was noted and analyzed. Further analysis would look to calculate price per milliliter (mL) of botulinum toxin and dermal filler per borough and to calculate whether there were any statistical differences between the 32 different London boroughs. RESULTS A total of 500 websites were visited and evaluated. After removal of duplicates, a total of 233 independent clinics was identified. A total of 206 out of the 233 clinics sampled (88%) were in direct infringement of the enforcement notice through advertising a prescription medicine. The overall average cost per mL of dermal filler was £330.89 and there was a statistically significant variance across London boroughs (p < 0.05). The overall average cost per mL of Botulinum Toxin was £284.45 and the variance across London boroughs was close to significant (p = 0.058). CONCLUSION This paper demonstrates poor compliance with the ASA/CAP guidelines and further provides an insight into the industry mechanics associated with aesthetic injectables in a major UK city, identifying regional variance in price and clinic density. The advertising of prescription-only medication may pose a potential risk to patients and will be an important consideration in proposed legislation to introduce licensing to the industry.
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Complications of Cosmetic Botulinum Toxin A Injections to the Upper Face: A Systematic Review and Meta-Analysis. Aesthet Surg J 2022; 42:NP327-NP336. [PMID: 35178552 PMCID: PMC9005453 DOI: 10.1093/asj/sjac036] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Background Botulinum toxin A (BoNT-A) injections are a popular non-surgical procedure for facial rejuvenation. Its increase in popularity and utilization is met with limited regulations, potentially posing a significant risk to patient safety and public health. Objectives The authors sought to assess the safety profile of cosmetic glabellar and forehead BoNT-A injections and evaluate BoNT-A type on complication rate. Methods A systematic search of MEDLINE and EMBASE was performed for studies reporting complications after cosmetic BoNT-A in the glabellar or in the forehead region in the glabellar or in the forehead region. A random effects meta-analysis was carried out to assess complication rate. Where there were sufficient randomized-controlled trials, a network meta-analysis was performed. Results Of 556 identified articles, 24 were included in the final quantitative analysis, with 4268 BoNT-A injection sessions and 1234 placebos. Frequently observed treatment-related complications in the BoNT-A intervention group included headache, local skin reactions, and facial neuromuscular symptoms. The overall BoNT-A complication rate was 16%. The odds ratio of developing complications from abobotulinum toxin injections compared with placebo was 1.62 (1.15, 2.27; P > 0.05) and that from onabotulinum toxin injections compared with placebo was 1.34 (0.52, 3.48; P > 0.05). In 30% of the studies, the injectors were doctors, whereas the training status of the practitioner was not reported in the remaining 70%. Conclusions Cosmetic BoNT-A injections in the glabellar and forehead region appear to be safe, and most complications are mild and transient. Nevertheless, the literature demonstrates heterogeneous reporting of complications and a lack of consistency of the definition of treatment-related complications. Level of Evidence: 2
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A consecutive series of targeted muscle reinnervation (TMR) cases for relief of neuroma and phantom limb pain: UK perspective. J Plast Reconstr Aesthet Surg 2021; 75:960-969. [PMID: 34840118 DOI: 10.1016/j.bjps.2021.09.068] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Revised: 07/12/2021] [Accepted: 09/27/2021] [Indexed: 01/07/2023]
Abstract
BACKGROUND Studies have suggested that targeted muscle reinnervation (TMR) can improve symptoms of neuroma pain (NP) and phantom limb pain (PLP) in patients. OBJECTIVES Our primary objective was to measure changes in NP and PLP levels following TMR surgery at 4-time points (baseline, 3, 6- and 12-months postoperatively). Secondary aims included identification of the character and rate of any surgical complications and patients' satisfaction with TMR. METHODS A retrospective review of outcomes of 36 patients who underwent TMR surgery to treat intractable NP and/or PLP after major amputation of an upper (UL) or lower limb (LL) at a single centre in London, UK over 7 years. The surgical techniques, complications, and satisfaction with TMR are described. RESULTS Forty TMR procedures were performed on 36 patients. Thirty patients had complete data for NP and PLP levels at all pre-defined time points. Significant improvements (p<0.01) in both types of pain were observed for both upper and LL amputees. However, there were varying patterns of recovery. For example, UL amputees experienced worsening of PLP in the first few months post-operatively whereas surgical complications were more common in LL cases. Patients were overwhelmingly satisfied with the improvements in their symptoms (90%). CONCLUSIONS TMR surgery appeared to relieve both NP and PLP although the retrospective nature of this study limits the strength of this conclusion. However, complication rates were high, and it is crucial for surgeons and patients to fully understand the course and outcomes of this novel surgery prior to undertaking treatment.
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1106 Timing of Free Flap Reconstruction in Sarcoma Patients. Br J Surg 2021. [DOI: 10.1093/bjs/znab259.719] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Abstract
Aim
In 1986 Godina reported that microsurgical reconstruction of traumatic wounds in the extremities undertaken with >72-hour delay caused significant tissue damage, hampering the microsurgical reconstruction and significantly increasing complication rates. It is our opinion that surgical treatment of sarcoma in the extremity is comparable to trauma surgery, given the extent of tissue destruction. The nature of sarcoma management often means that performing definitive reconstruction within 72 hours is not possible. We analyse the outcomes of our ‘delayed’ extremity reconstruction.
Method
We performed a retrospective analysis of 52 consecutive cases of free flap extremity reconstruction following sarcoma excision. Data was analysed for time from resection to reconstruction, significant patient demographics, details of the flap and post-operative complications.
Results
Between March 2017 and December 2020, we performed 52 free flaps for sarcoma reconstruction in the extremities. Mean time to reconstruction was 28 days (Median 15 days, Range: 0-316 days), with two reconstructions within 72 hours of excision. 9 patients had neoadjuvant chemo- or radiotherapy. Three patients had significant post-operative complications; two flaps failed intra-operatively (3.8%) and one patient (1.9%) experienced wound infection.
Conclusions
Godina’s study demonstrated the negative impact of delaying surgical reconstruction in the traumatised extremity, with a 12% failure and 17.5% infection rate in delayed reconstruction (72 hours to 3 weeks). Our results show that with advancements in microsurgical techniques and physiological optimization, it is possible to safely and successfully undertake delayed (>72 hours) microsurgical extremity reconstruction in sarcoma patients and achieve low flap failure and infection rates.
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Extensive non-redundancy in a recently duplicated developmental gene family. BMC Ecol Evol 2021; 21:33. [PMID: 33648446 PMCID: PMC7919330 DOI: 10.1186/s12862-020-01735-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Accepted: 12/13/2020] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND It has been proposed that recently duplicated genes are more likely to be redundant with one another compared to ancient paralogues. The evolutionary logic underpinning this idea is simple, as the assumption is that recently derived paralogous genes are more similar in sequence compared to members of ancient gene families. We set out to test this idea by using molecular phylogenetics and exploiting the genetic tractability of the model nematode, Caenorhabditis elegans, in studying the nematode-specific family of Hedgehog-related genes, the Warthogs. Hedgehog is one of a handful of signal transduction pathways that underpins the development of bilaterian animals. While having lost a bona fide Hedgehog gene, most nematodes have evolved an expanded repertoire of Hedgehog-related genes, ten of which reside within the Warthog family. RESULTS We have characterised their evolutionary origin and their roles in C. elegans and found that these genes have adopted new functions in aspects of post-embryonic development, including left-right asymmetry and cell fate determination, akin to the functions of their vertebrate counterparts. Analysis of various double and triple mutants of the Warthog family reveals that more recently derived paralogues are not redundant with one another, while a pair of divergent Warthogs do display redundancy with respect to their function in cuticle biosynthesis. CONCLUSIONS We have shown that newer members of taxon-restricted gene families are not always functionally redundant despite their recent inception, whereas much older paralogues can be, which is considered paradoxical according to the current framework in gene evolution.
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Pedicled ipsilateral anterolateral thigh (ALT) with flow-through to a secondary contralateral-free ALT flap for coverage of large thigh, trochanteric, and gluteal area defects: A case report. Microsurgery 2021; 41:276-279. [PMID: 33452821 DOI: 10.1002/micr.30706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 11/08/2020] [Accepted: 12/31/2020] [Indexed: 11/10/2022]
Abstract
Reconstruction of the trochanteric area can be difficult in extensive defects postsarcoma resection. It requires a robust flap. In reconstructing the upper thigh, trochanteric, and gluteal area, a pedicled anterolateral thigh (ALT) flap is a good option. If the defect extends further than the pivot point of a single pedicled ALT, this can be used a flow-through for a secondary free flap. Here we describe a case of a 66-year-old gentleman with a 25 cm × 15 cm defect in the trochanteric and gluteal area where a single pedicled ALT was insufficient for coverage and hence a second ALT from the contralateral leg is anastomosed to the distal runoff of the descending branch of the lateral circumflex femoral vessel of the pedicled ALT, using it as the flow-through donor vessel. This method requires less time if a second free flap is required and a smaller range of dissection, and it also facilitates anastomosis, as the vessel can be brought to the surface for anastomosis while supine before inset. The patient healed with no complications and received radiotherapy to the area. On 1-year follow-up, the area has healed well despite some contraction secondary to the radiotherapy. Using the pedicled ALT as a flow-through for a second free flap is a useful adjunct to large defects in the gluteal and trochanteric area, which is a difficult area to reconstruct with limited donor vessels.
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Safe pedicle tunnelling and retrieval for free flap surgery. Ann R Coll Surg Engl 2020; 102:754-755. [PMID: 32808801 DOI: 10.1308/rcsann.2020.0165] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Combinatorial model organism strategy to predict developmental and reproductive toxicology (DART). Toxicol Lett 2017. [DOI: 10.1016/j.toxlet.2017.07.258] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Abstract
Runx genes have been identified in all metazoans and considerable conservation of function observed across a wide range of phyla. Thus, insight gained from studying simple model organisms is invaluable in understanding RUNX biology in higher animals. Consequently, this chapter will focus on the Runx genes in the diploblasts, which includes sea anemones and sponges, as well as the lower triploblasts, including the sea urchin, nematode, planaria and insect. Due to the high degree of functional redundancy amongst vertebrate Runx genes, simpler model organisms with a solo Runx gene, like C. elegans, are invaluable systems in which to probe the molecular basis of RUNX function within a whole organism. Additionally, comparative analyses of Runx sequence and function allows for the development of novel evolutionary insights. Strikingly, recent data has emerged that reveals the presence of a Runx gene in a protist, demonstrating even more widespread occurrence of Runx genes than was previously thought. This review will summarize recent progress in using invertebrate organisms to investigate RUNX function during development and regeneration, highlighting emerging unifying themes.
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Dual-consultant led elective microsurgery: the implications on service provision and training. J Plast Reconstr Aesthet Surg 2013; 66:1435-6. [PMID: 23623271 DOI: 10.1016/j.bjps.2013.04.040] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2013] [Accepted: 04/04/2013] [Indexed: 11/19/2022]
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Q06 Multivariate classification of central nervous system-acting drugs based on in vivo response patterns – profile of pridopidine. Journal of Neurology, Neurosurgery and Psychiatry 2012. [DOI: 10.1136/jnnp-2012-303524.176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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The association of hypothalamic-pituitary-adrenal axis activity and blood pressure in an Afro-Caribbean population. Psychoneuroendocrinology 2009; 34:736-42. [PMID: 19155140 DOI: 10.1016/j.psyneuen.2008.12.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/24/2008] [Revised: 12/08/2008] [Accepted: 12/09/2008] [Indexed: 10/21/2022]
Abstract
Hyperactivity of the hypothalamic-pituitary-adrenal axis (HPAA) resulting from fetal programming may play a role in the development of high blood pressure (BP) in black people. We assessed the diurnal salivary cortisol profile in children with and without increased BP and evaluated their mother's HPAA. In a cross-sectional study, 20 Afro-Caribbean children (mean age 9.6 years) with higher blood pressures and 20 children with lower blood pressures were chosen from a prospective study of 569 mothers and children in Jamaica. Daytime salivary cortisol profiles were collected in the children and their mothers. The mothers were also assessed for features of the metabolic syndrome. Children with higher BP had higher mean morning salivary cortisol concentrations than those with lower BP (7.9 S.D. 1.9 vs. 4.5 S.D. 2.4nmol/l; p=0.03). Their mothers also had increased morning salivary cortisol concentrations (9.9 S.D. 1.8 vs. 5.5 S.D. 2.5nmol/l; p=0.02), but no changes in fasting glucose, insulin, lipids, BP or adiposity. Maternal and offspring cortisol concentrations correlated significantly (r=0.465, p=0.004). Maternal cortisol concentrations were significantly associated with the child's BP. We conclude that Afro-Caribbean children with higher BP have higher morning salivary cortisol concentrations. The children's cortisol concentrations correlate significantly with the mother's cortisol concentrations. These findings suggest that the HPAA may play a role in the development of raised BP in Afro-Caribbean people.
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The caenorhabditis elegans fate-determining gene mab-9 encodes a T-box protein required to pattern the posterior hindgut. Genes Dev 2000; 14:596-603. [PMID: 10716947 PMCID: PMC316422] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/1999] [Accepted: 01/27/2000] [Indexed: 02/15/2023]
Abstract
Caenorhabditis elegans mab-9 mutants are defective in hindgut and male tail development because of cell fate transformations in two posterior blast cells, B and F. We have cloned mab-9 and show that it encodes a member of the T-box family of transcriptional regulators. MAB-9 localizes to the nucleus of B and F and their descendents during development, suggesting that it acts cell autonomously in the posterior hindgut to direct cell fate. T-box genes related to brachyury have also been implicated in hindgut patterning, and our results support models for an evolutionarily ancient role for these genes in hindgut formation.
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Analysis of the cps1 gene provides evidence for a septation checkpoint in Schizosaccharomyces pombe. MOLECULAR & GENERAL GENETICS : MGG 1999; 262:163-72. [PMID: 10503548 DOI: 10.1007/s004380051071] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
The fission yeast gene cps1, which encodes the catalytic subunit of beta-glucan synthase, was isolated in a screen for mutants that show an increase in ploidy at the restrictive temperature. cps1 mutants display defects in both polarity and septation at the permissive temperature, and become swollen and multinucleate at the restrictive temperature. Analysis of the interaction of cps1 with other mutations suggests the existence of a septation checkpoint, which requires the activity of the protein kinase weel for function.
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Stu-7/air-2 is a C. elegans aurora homologue essential for chromosome segregation during embryonic and post-embryonic development. Mech Dev 1999; 82:95-108. [PMID: 10354474 DOI: 10.1016/s0925-4773(99)00020-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
We have isolated a new sterile uncoordinated C. elegans mutant, stu-7, which is defective in post-embryonic cell divisions in a regionally-specific fashion. The anterior of the worm is relatively unaffected whereas the mid-body and/or posterior are markedly thin, often resulting in worms having a central 'waist'. We have cloned stu-7 and found that it encodes a member of the recently expanding aurora sub-family of serine/threonine kinases. Elimination of maternal as well as zygotic stu-7 expression reveals that stu-7 is essential for mitosis from the first embryonic cell cycle onwards and is required for chromosome segregation though not for centrosome separation or for setting up a bipolar spindle. Multicopy expression of stu-7 also causes mitotic defects, suggesting that the level of this protein must be tightly controlled in order to maintain genetic stability during development.
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The Spg1p GTPase is an essential, dosage-dependent inducer of septum formation in Schizosaccharomyces pombe. Genes Dev 1997; 11:1519-34. [PMID: 9203579 DOI: 10.1101/gad.11.12.1519] [Citation(s) in RCA: 176] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The spg1 gene (septum-promoting GTPase) was cloned as a multicopy suppressor of a dominant-negative mutant of the Cdc7p kinase. It encodes a small GTPase of the Ras superfamily. spg1 is an essential gene. Null or heat-sensitive alleles do not make a division septum, but growth, S-phase, and mitosis continue in the absence of cell division, producing elongated, multinucleate cells. Increased expression of Spg1p induces septum formation in G2, S-phase, and pre-Start G1-arrested cells. This requires the activity of Cdc7p kinase, but not p34(cdc2). Increased expression of Cdc7p bypasses the requirement for Spg1p. Spg1p and Cdc7p can be coimmunoprecipitated from cell extracts, and interact in the two-hybrid system. These data indicate that Spg1p is a key element in controlling the onset of septum formation in Schizosaccharomyces pombe, and that it acts through the Cdc7p kinase.
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A novel S phase inhibitor in fission yeast. EMBO J 1996; 15:4603-12. [PMID: 8887552 PMCID: PMC452191] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
We have cloned a novel fission yeast gene, spd1, which causes G1 arrest when overexpressed. Deleting the gene results in cells being accelerated through G1 into S phase in certain circumstances when the G1-->S phase control is compromised. We have found that the encoded 14 kDa protein is cell cycle regulated, declining in level during S phase, and that p14spd1 physically associates with p34cdc2 in vivo when overexpressed, suggesting that p14spd1 may regulate S phase progression via an interaction with p34cdc2. We conclude that p14spd1 is a negative regulator of S phase, and that it may be part of the control ensuring an orderly onset of S phase or part of a G1-->S phase checkpoint control.
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Isolation and characterization of fission yeast mutants defective in the assembly and placement of the contractile actin ring. J Cell Sci 1996; 109 ( Pt 1):131-42. [PMID: 8834798 DOI: 10.1242/jcs.109.1.131] [Citation(s) in RCA: 253] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Fission yeast cells divide by medial cleavage using an actin-based contractile ring. We have conducted a genetic screen for temperature-sensitive mutants defective in the assembly and placement of this actin ring. Six genes necessary for actin ring formation and one gene necessary for placement of the actin ring have now been identified. The genes can be further organized into different phenotypic groups, suggesting that the gene products may have different functions in actin ring formation. Mutants of cdc3 and cdc8, which encode profilin and tropomyosin respectively, display disorganized actin patches in all cells. cdc12 and cdc15 mutants display disorganized actin patches during mitosis, but normal interphase actin patterns. cdc4 and rng2 mutants display disorganized actin cables during mitosis, but normal interphase actin patterns. In mid1 mutants, the actin ring and septum are positioned at random locations and angles on the cell surface, although the nucleus is positioned normally, indicating that the mid1 gene product is required to couple the division site to the position of the nucleus. mid1 mutant cells may reveal a new cell cycle checkpoint in telophase that coordinates cell division and the proper distribution of nuclei. The actin ring forms medially in a beta-tubulin mutant, showing that actin ring formation and placement are not dependent on the mitotic spindle.
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Abstract
Three major aspects of G1 regulation acting at START in fission yeast are discussed in this review. Firstly, progression towards S phase in the mitotic cycle. This is controlled by the activation of transcription complexes at START which cause cell cycle-dependent activation of genes required for DNA synthesis. The second aspect is the regulation of developmental fate occurring during G1. Passage through START appears to inhibit sexual differentiation because the meiotic and mitotic pathways are mutually exclusive. This is brought about because the meiotic pathway is inhibited by the same gene functions that are required for S phase onset. Thirdly, distinct checkpoint, or dependency, controls operate both pre- and post-START in the mitotic cycle to inhibit mitosis in the absence of replicated DNA, and also to limit rounds of DNA replication to one per cell cycle.
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Temporal order of S phase and mitosis in fission yeast is determined by the state of the p34cdc2-mitotic B cyclin complex. Cell 1994; 78:813-22. [PMID: 8087848 DOI: 10.1016/s0092-8674(94)90542-8] [Citation(s) in RCA: 320] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We show here that the state of the p34cdc2-p56cdc13 mitotic B cyclin complex determines whether a fission yeast cell undergoes S phase or mitosis. Mutants defective for p56cdc13 reset to G1 and rereplicate their DNA, while cells completely lacking the p34cdc2-p56cdc13 complex undergo multiple rounds of S phase. In contrast, formation of the p34cdc2-p56cdc13 complex in G1 promotes cells inappropriately into mitosis. We propose that the temporal order of S phase and mitosis is maintained by the presence or absence of the p34cdc2-p56cdc13 complex.
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