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1.
Ann Chir Plast Esthet ; 64(5-6): 511-518, 2019 Nov.
Article in French | MEDLINE | ID: mdl-31445778

ABSTRACT

Facial recontouring has always been a longstanding objective of esthetic or reconstructive surgery. Most often it uses two types of surgical techniques: autologous and alloplastic. In that regard, different surgical techniques have been proposed to enhance facial recontouring. MATERIALS AND METHODS: Through 5 clinical case reports and a literature review, this article explores the use of allopastic microporous titanium implants in secondary volumetric corrections of the face. RESULTS: There is a current lack of evidence regarding the use of microporous titanium implants in volumetric corrections of the face, most papers reporting their use in post-traumatic or post-surgical cranio-facial defects repair. DISCUSSION: Pros and cons of such implants are discussed in association with the usefulness of this surgical technique in daily surgical practice.


Subject(s)
Facial Bones/surgery , Plastic Surgery Procedures/methods , Prostheses and Implants , Reoperation , Titanium , Adult , Female , Humans , Middle Aged , Porosity , Young Adult
2.
Opt Express ; 25(15): 16957-16970, 2017 Jul 24.
Article in English | MEDLINE | ID: mdl-28789195

ABSTRACT

The Petawatt Aquitaine Laser (PETAL) facility was designed and constructed by the French Commissariat à l'énergie atomique et aux énergies alternatives (CEA) as an additional PW beamline to the Laser MegaJoule (LMJ) facility. PETAL energy is limited to 1 kJ at the beginning due to the damage threshold of the final optics. In this paper, we present the commissioning of the PW PETAL beamline. The first kJ shots in the amplifier section with a large spectrum front end, the alignment of the synthetic aperture compression stage and the initial demonstration of the 1.15 PW @ 850 J operations in the compression stage are detailed. Issues encountered relating to damage to optics are also addressed.

3.
J La State Med Soc ; 169(2): 57, 2017.
Article in English | MEDLINE | ID: mdl-28414686

ABSTRACT

BACKGROUND: A diagnosis of severe sepsis or septic shock has been shown to significantly increase mortality rate independent of other factors. Research has revealed all cause hospital case fatality rates have declined yet the percentage of severe sepsis cases continues to increase and age-adjusted mortality rates from severe sepsis and septic shock has significantly increased during the same time period. Patients with severe sepsis demonstrate ongoing mortality rate increases for up to 2 years following hospitalization when compared to aged matched controls of nonseptic patients. International guidelines with mortality benefit for the management of severe sepsis and septic shock have been illustrated in the latest surviving sepsis campaign. OBJECTIVE: The objective of this study was to increase the percentage of patients admitted to the hospital with a diagnosis of severe sepsis or septic shock who met guidelines based on surviving sepsis campaign. METHODOLOGY: A retrospective chart review was conducted for patients admitted to UHC from January 2016 to present to identify cases with a diagnosis of severe sepsis or septic shock, and whether they met guidelines set forth by surviving sepsis campaign both before and after an intervention program which included interviews with providers failing to meet protocol, educational sessions on guidelines to meet protocol, resident led quality improvement workshops to address barriers to meeting protocol, and development of an EMR power plan to assist providers on meeting protocol. RESULTS: 139 cases with a diagnosis, or meeting criteria for, severe sepsis or septic shock were identified during the period of 1/1/2016-9/30/2016 with an average of 43 percent of total cases which met guidelines. Trend analysis revealed increased compliance following resident lead intervention program with 31 percent and 49 percent before and after intervention, respectively. ICU data is currently being analyzed for meeting guidelines and have not been included in current data. The most common reason for failing guidelines was failure to obtain or repeat lactic acid on time (46 percent ); and failure to give timely antibiotics (22 percent );. CONCLUSIONS: The percentage of patients admitted to the hospital with a diagnosis of severe sepsis or septic shock at UHC meeting guidelines set forth by surviving sepsis campaign has improved following resident lead intervention program. Intervention strategies to further improve compliance with guidelines with a goal >60 percent are currently being analyzed.

4.
Eur J Clin Microbiol Infect Dis ; 34(11): 2225-34, 2015 Nov.
Article in English | MEDLINE | ID: mdl-26337432

ABSTRACT

Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) has been introduced as an identification procedure for bacteria and fungi. The MALDI-TOF MS-based analysis of resistance to ß-lactam antibiotics has been applied to detect hydrolysis of carbapenems by different bacterial strains. However, the detection of enzymatic carbapenem degradation by MALDI-TOF MS lacks well-standardized protocols and several methods and models of interpretation using different calculations of ratio-of-peak intensities have been described in the literature. Here, we used faropenem and ertapenem hydrolysis as model compounds. In an attempt to propose a universal protocol, the hydrolysis was regularly monitored during 24 h using well-characterized bacterial strains producing different types of carbapenemases (KPC, IMP, NDM, VIM, and OXA-48). Variable responses and different timing for detectable hydrolysis, depending on the enzyme produced, were observed. KPC degrades its template antibiotics very quickly (15 min for some KPC producers) compared to other types of enzymes (more than 90 min for other enzymes). Prior bacterial lysis was shown to be of no interest in the modulation or optimization of the hydrolytic kinetics. The adequate detection of carbapenem hydrolysis would, therefore, require several MALDI-TOF MS readouts for the timely detection of rapid hydrolysis without missing slow hydrolysis. This enzymatic constraint limits the implementation of a standard protocol in routine microbiology laboratories.


Subject(s)
Anti-Bacterial Agents/metabolism , Bacterial Proteins/analysis , Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization/methods , beta-Lactamases/analysis , Ertapenem , Fungi , Humans , Hydrolysis , Kinetics , Time Factors , beta-Lactams/metabolism
5.
Atmos Chem Phys ; 12(5): 11317-11350, 2012 May 03.
Article in English | MEDLINE | ID: mdl-23393494

ABSTRACT

The rate of consumption of dithiothreitol (DTT) is increasingly used to measure the oxidative potential of particulate matter (PM), which has been linked to the adverse health effects of PM. While several quinones are known to be very reactive in the DTT assay, it is unclear what other chemical species might contribute to the loss of DTT in PM extracts. To address this question, we quantify the rate of DTT loss from individual redox-active species that are common in ambient particulate matter. While most past research has indicated that the DTT assay is not sensitive to metals, our results show that seven out of the ten transition metals tested do oxidize DTT, as do three out of the five quinones tested. While metals are less efficient at oxidizing DTT compared to the most reactive quinones, concentrations of soluble transition metals in fine particulate matter are generally much higher than those of quinones. The net result is that metals appear to dominate the DTT response for typical ambient PM(2.5) samples. Based on particulate concentrations of quinones and soluble metals from the literature, and our measured DTT responses for these species, we estimate that for typical PM(2.5) samples approximately 80 % of DTT loss is from transition metals (especially copper and manganese), while quinones account for approximately 20 %. We find a similar result for DTT loss measured in a small set of PM(2.5) samples from the San Joaquin Valley of California. Because of the important contribution from metals, we also tested how the DTT assay is affected by EDTA, a chelator that is sometimes used in the assay. EDTA significantly suppresses the response from both metals and quinones; we therefore recommend that EDTA should not be included in the DTT assay.

6.
Anal Chem ; 81(22): 9343-52, 2009 Nov 15.
Article in English | MEDLINE | ID: mdl-19839594

ABSTRACT

Mass spectrometry-based strategies for the quantification of low-abundance putative protein biomarkers in human blood currently require extensive sample fractionation steps which hamper their implementation in a routine and robust way across clinical laboratories. We demonstrate that a technique using MS(3) reconstructed chromatograms on a signature of secondary ions issued from a trapped primary product ion, termed multiple reaction monitoring cubed (MRM(3)), enables targeting protein biomarkers in the low nanogram/milliliter range in nondepleted human serum. The simple two-step workflow is based on a trypsin proteolysis of whole serum (100 microL) followed by enrichment of targeted proteotypic peptides on a solid phase extraction column using mixed-cation exchange resin. MRM(3)'s fidelity of peak detection extends the dynamic range and limit of quantitation (LOQ) of protein biomarkers to the low nanogram/milliliter range, corresponding to a concentration that is 10(6)-fold lower than the concentration of the most abundant proteins in serum. The power of the MRM(3) method is illustrated by the assay of prostate specific antigen in nondepleted human sera of patients. The results correlate well with the established method for determining PSA levels in serum, i.e., enzyme-linked immunosorbent assay (ELISA) tests.


Subject(s)
Biomarkers, Tumor/blood , Chemistry Techniques, Analytical/methods , Chromatography, Liquid/methods , Prostate-Specific Antigen/blood , Prostatic Neoplasms/blood , Tandem Mass Spectrometry/methods , Female , Humans , Male , Sensitivity and Specificity
7.
J Fr Ophtalmol ; 32(5): 352-6, 2009 May.
Article in French | MEDLINE | ID: mdl-19769874

ABSTRACT

Neonatal obstruction of the distal part of the lachrymal system can lead to dilatation of the lachrymal sac if associated with a canaliculus problem. Clinical presentation is a blue tumor of the internal canthus. This external expansion of the lachrymal sac communicates with a nasal expansion under the inferior nasal turbinate. Even if this typical presentation is spectacular, spontaneous resolution occurs in 80% of cases. There are two main types of progression: an abscess of the lachrymal sac can occur (20%) or bilateral nasal respiratory obstruction in cases of bilateral obstacle because newborns are obligatory nose breathers (<0.1%).


Subject(s)
Lacrimal Duct Obstruction , Humans , Infant, Newborn , Lacrimal Duct Obstruction/diagnosis , Lacrimal Duct Obstruction/physiopathology , Lacrimal Duct Obstruction/therapy
10.
Arch Pediatr ; 15(4): 473-6, 2008 Apr.
Article in French | MEDLINE | ID: mdl-18314315

ABSTRACT

Congenital cervical cysts, sinuses and fistulae are uncommon malformations. Diagnosis and management of congenital cervical cysts, sinuses and fistulae requires a good understanding of their embryological development and topography. Thyroglossal duct cysts are most common, followed by branchial cleft anomalies and dermoid cysts. In this review, we discuss both the classical and current aspects of these malformations.


Subject(s)
Cysts/congenital , Fistula/congenital , Head , Neck , Paranasal Sinus Diseases/congenital , Female , Humans , Infant, Newborn , Male
11.
Rev Laryngol Otol Rhinol (Bord) ; 129(4-5): 313-8, 2008.
Article in English | MEDLINE | ID: mdl-19408518

ABSTRACT

AIM OF THE STUDY: Parotidectomy leaves a retromandibular hollow area in proportion with the amount of gland resected. Many surgeons perform primary reconstruction after superficial or subtotal parotidectomy in patients with exo-facial pleiomorphic focal adenoma. Many techniques have been proposed. We present a new technique of filling of the parotidectomy chamber by a second generation leucocyte and platelet concentrate, Platelet-Rich Fibrin (PRF, Choukroun's method). PATIENTS AND METHODS: 10 patients were included in this preliminary study. Subtotal parotidectomy was performed through classic procedure or lifting procedure. The macroscopic security margin of resection usually allowed performance of a SMAS flap. PRF was prepared following the original Choukroun's method. RESULTS AND DISCUSSION: PRF slow resorption after filling of the exeresis cavity, offers a key aesthetic interest. The fibrin matrix of this biomaterial has many angiogenic and healing properties. Synergetic action of the fibrin and the platelets cytokines within PRF may improve revascularization and postoperative resumption of facial nerve function. The membrane formed by the fibrin dense fibrillary network, as well as the SMAS flap, may help to prevent the Frey's syndrome. CONCLUSION: We propose the use of PRF as a filling, healing and interposition material after parotidectomy for benign parotid tumors. Preliminary results are very encouraging. Longer prospective evaluation of this technique is necessary.


Subject(s)
Adenoma/surgery , Biocompatible Materials , Blood Platelets , Fibrin , Parotid Neoplasms/surgery , Plastic Surgery Procedures/methods , Surgical Flaps , Adult , Humans , Middle Aged , Otorhinolaryngologic Surgical Procedures/methods
12.
Ann Chir Plast Esthet ; 53(3): 281-4, 2008 Jun.
Article in French | MEDLINE | ID: mdl-17408836

ABSTRACT

The facial artery musculomucosal flap (FAMM) is usually used in reconstruction of defects in oral cavity, most frequent being the mouth floor. This flap has many advantages from its surgical procedure, its great reliability, its mucous tissue origin, its usable surface, its large axis of rotation and the little of after-effects of the donor site. The hard palate defects with bucconasal communication can raise difficulties of reconstruction. We show, by a case report, the many advantages of FAMM flap in these reconstructions.


Subject(s)
Mouth Floor/abnormalities , Mouth Floor/surgery , Palate, Hard/abnormalities , Palate, Hard/surgery , Plastic Surgery Procedures , Face/blood supply , Humans , Muscle, Skeletal/transplantation , Surgical Flaps
13.
Article in English | MEDLINE | ID: mdl-17728194

ABSTRACT

Many problems concerned with the production and the purification of recombinant proteins must be addressed prior to launching an industrial production process. Among these problems, attention is focused on low-level expression that complicates the purification step and can jeopardise the process. The expression of a membrane protein, rP30, of Toxoplasma gondii in the yeast Schizosaccharomyces pombe led to a secretion of only 0.5 microg ml(-1). In order to obtain a sufficient quantity for biochemical characterization and evaluation in vitro diagnostic test development, strategies for both production and purification had to be optimized. First, the influence of four nitrogen sources (three peptones and yeast extract) on the growth rate, but also on the separation between the protein and the components of the fermentation broth was assessed. Second, batch and fed-batch fermentations were compared in terms of final biomass and rP30 concentrations. Third, three different protocols that included fixed and expanded bed ion exchange chromatography were compared for processing a large volume of feedstock. By using the most appropriate strategies, i.e. fed-batch fermentation, capture on EBA cation exchanger and affinity chromatography polishing, a purification factor of 1778 and a yield of 49% were achieved. These performances allowed a 12.5-fold increase for the overall rP30 process productivity.


Subject(s)
Antigens, Protozoan/isolation & purification , Protozoan Proteins/isolation & purification , Recombinant Proteins/isolation & purification , Toxoplasma/metabolism , Animals , Antigens, Protozoan/genetics , Antigens, Protozoan/metabolism , Biomass , Chromatography, Affinity/methods , Fermentation , Protozoan Proteins/genetics , Protozoan Proteins/metabolism , Recombinant Proteins/metabolism , Schizosaccharomyces/genetics , Schizosaccharomyces/metabolism , Toxoplasma/genetics
14.
Int J Pediatr Otorhinolaryngol ; 70(11): 1949-55, 2006 Nov.
Article in English | MEDLINE | ID: mdl-16950520

ABSTRACT

OBJECTIVES: The authors describe 28 pediatric cases of foreign body inhalation requiring treatment in intensive care units between 1987 and 1999. The purpose of this study was: (1) to analyze the circumstances, diagnostic difficulties and initial treatment of serious foreign bodies and (2) to compare our series with other literature descriptions and define principles for optimal prevention and initial treatment. METHODS: Twenty-one children presented a penetration syndrome, which was responsible in 13 cases for asphyxia with cardiorespiratory arrest. All these children died, regardless of the initial treatment. Seven children were hospitalized for apparent asthmatic symptoms that did not respond to traditional treatment. RESULTS: The inefficiency of external extraction methods like the Heimlich maneuver and the mean delay between clinical signs and initial treatment lead us to propose a new strategy for the emergency treatment of foreign bodies with asphyxia. CONCLUSIONS: We recommend that emergency teams promote the use of a laryngoscope and Magill forceps. Flexible endoscopy is still recommended as the appropriate diagnostic tool to eliminate doubt in the case of a first severe asthma attack.


Subject(s)
First Aid/methods , Foreign Bodies/epidemiology , Foreign Bodies/therapy , Respiratory System/physiopathology , Child , Child, Preschool , Female , Foreign Bodies/mortality , France/epidemiology , Humans , Incidence , Infant , Male
15.
Rev Stomatol Chir Maxillofac ; 107(1): 44-9, 2006 Feb.
Article in French | MEDLINE | ID: mdl-16523177

ABSTRACT

INTRODUCTION: Nasal gliomas or heterotopia are nonhereditary congenital malformations composed of heterotopic neuroglial tissue. They usually present in infancy. Evaluation should include preoperative imaging with CT scan and/or MRI to rule out intracranial extension. There have been several cases reported in which nasal gliomas were misdiagnosed as capillary hemangiomas. The differential diagnosis includes prenasal space developmental impairment, which are nasoethmoidal meningoencephaloceles, nasal dermoid and epidermoid cysts. CASE REPORT: We describe the case of a newborn male infant presenting at birth with a paramedial nasal glioma. An embryological and clinical analysis of nasal gliomas is proposed. DISCUSSION: Nasal glioma is an uncommon congenital lesion presenting as a large panel of midline craniofacial anomalies. The embryological and anatomical origins of nasal gliomas are reviewed. The most known embryological theory was described by Grünwald in 1910 and is called the "prenasal space" theory. This theory is very attractive because of the embryopathogenic continuum proposed among dermoids, gliomas, and encephaloceles. In this article, we discuss major embryological theories on nasal gliomas pathogenesis and propose that while the prenasal space theory can explain the occurrence and the continuum between basal anterior or prenasal encephaloceles and gliomas, it cannot explain the occurrence of craniofacial demoids of the same topography. Better knowledge of embryological mechanisms implicated in the pathogenesis of nasal gliomas can help clinical management of this kind of malformations.


Subject(s)
Choristoma/congenital , Neuroglia/pathology , Nose Diseases/congenital , Choristoma/embryology , Diagnosis, Differential , Glioma/congenital , Hemangioma, Capillary/congenital , Humans , Infant, Newborn , Male , Nose Diseases/embryology , Nose Neoplasms/congenital
16.
Ann Otolaryngol Chir Cervicofac ; 122(1): 3-17, 2005 Feb.
Article in French | MEDLINE | ID: mdl-15851940

ABSTRACT

Idiopathic Sudden Sensorineural Hearing Loss (ISSHL) remains one of the major unsolved otologic emergencies. It is characterized by the onset of an unilateral sensorineural hearing loss developing within 24 hours, and averaging on pure tone audiogram at least 30 dB HL for three subsequent octave steps, with no marked vestibular symptoms and no identifiable cause. ISSHL is a syndrome covering several heterogeneous entities resulting from different pathogenetic mechanisms. At this time, the audiogram is the unique tool which may help clinicians to identify these entities and provide a classification based on 5 types of hearing loss. Numerous experimental and clinical studies have investigated the mechanisms by which infectious, ischemic, mechanic or immunologic insults may induce cochlear dysfunction. However, extrapolation to humans and rationale therapeutic approaches to ISSHL remain uncertain. SSHL being a diagnosis of exclusion, retrocochlear and neurologic etiologies should be eliminated. No argument allows to consider ISSHL a therapeutic emergency. More precisely, the experimental data presently available on cochlear physiology suggests that a treatment could have some chance to be effective if undertaken within minutes following the onset of ISSHL, a condition never encountered in daily practice. Conversely, it is not justifiable to impute the absence of hearing recovery to a delay in therapy. The various therapeutic strategies currently recommended are highly empirical and should be questionned in terms of cost-effectiveness, the most common being high-dose corticosteroids. New investigation tests are required for improving our approach to ISSHL.


Subject(s)
Hearing Loss, Sensorineural , Diagnosis, Differential , Hearing Loss, Sensorineural/diagnosis , Hearing Loss, Sensorineural/etiology , Hearing Loss, Sensorineural/therapy , Humans , Prognosis
17.
Ann Otolaryngol Chir Cervicofac ; 120(6): 315-29, 2003 Dec.
Article in French | MEDLINE | ID: mdl-14730276

ABSTRACT

Nasal dermoid sinus cyst (NDSC) is an uncommon congenital lesion presenting as a large panel of midline craniofacial anomalies. Thirty children with nasal midline masses and/or sinus ostia were surgically treated in the pediatric ENT and cervicofacial surgery department of Trousseau's children's hospital (Paris-France) between 1995 and 2002. All our patients underwent radiological evaluation including CT scan (including axial and coronal planes) and/or MRI (in all three planes) in search of intracranial extension. Thirteen of our patients presented with a midline cyst only, ten had nasal pit only, and seven had combined anomalies. Preoperative radiology and surgery showed an intracranial extension in 3 patients, which exhibited contact of the cyst with the dura. Recurrence being expected if any dermal tissues were left in place, "one-time-excision management" was the rule. CT and MR imaging features were reviewed. The external rhinoplasty procedure resulted in a wide surgical approach, low recurrence and good esthetic results. The embryological and anatomical origins of NDSCs are reviewed. Development of NDSC during embryological development implicates two necessary and sufficient conditions: competence of the ectodermal and mesectodermal cells to form dermoid tissue with epithelial-mesenchymal interactions, and a topographical site of ectodermal inclusion, which fits well with the various clinical presentations of NDSCs. We propose to distinguish NDSCs of anterior topography, located at the anterior skull base level from the basal NDSCs, located at the middle skull base level. We reviewed the various localizations of NDSCs, revisiting a forgotten embryological theory, which unify the various clinical localizations of anterior NDSCs.


Subject(s)
Cutaneous Fistula/embryology , Cutaneous Fistula/surgery , Cysts/embryology , Cysts/surgery , Nose Diseases/embryology , Nose Diseases/surgery , Respiratory Tract Fistula/embryology , Respiratory Tract Fistula/surgery , Adolescent , Child , Child, Preschool , Female , Humans , Infant , Male
18.
Development ; 128(24): 5139-47, 2001 Dec.
Article in English | MEDLINE | ID: mdl-11748149

ABSTRACT

In the vertebrate embryo, segmentation is built on repetitive structures, named somites, which are formed progressively from the most rostral part of presomitic mesoderm, every 90 minutes in the avian embryo. The discovery of the cyclic expression of several genes, occurring every 90 minutes in each presomitic cell, has shown that there is a molecular clock linked to somitogenesis. We demonstrate that a dynamic expression pattern of the cycling genes is already evident at the level of the prospective presomitic territory. The analysis of this expression pattern, correlated with a quail/chick fate-map, identifies a 'wave' of expression travelling along the future medial/lateral presomitic axis. Further analysis also reveals the existence of a medial/lateral asynchrony of expression at the level of presomitic mesoderm. This work suggests that the molecular clock is providing cellular positional information not only along the anterior/posterior but also along the medial/lateral presomitic axis. Finally, by using an in vitro culture system, we show that the information for morphological somite formation and molecular segmentation is segregated within the medial/lateral presomitic axis. Medial presomitic cells are able to form somites and express segmentation markers in the absence of lateral presomitic cells. By contrast, and surprisingly, lateral presomitic cells that are deprived of their medial counterparts are not able to organise themselves into somites and lose the expression of genes known to be important for vertebrate segmentation, such as Delta-1, Notch-1, paraxis, hairy1, hairy2 and lunatic fringe.


Subject(s)
Avian Proteins , Birds/embryology , Body Patterning , Glycosyltransferases , Mesoderm , Somites , Animals , Basic Helix-Loop-Helix Transcription Factors , Biological Clocks , Cell Lineage , Chick Embryo , Coturnix , Homeodomain Proteins , In Vitro Techniques , Periodicity , Proteins/isolation & purification , Somites/transplantation , Transcription Factor HES-1 , Transcription Factors/isolation & purification
19.
Br J Oral Maxillofac Surg ; 39(5): 394-7, 2001 Oct.
Article in English | MEDLINE | ID: mdl-11601823

ABSTRACT

Alveolar soft-part sarcoma is a rare malignant tumour of uncertain histogenesis, the two main sites of which are the lower extremities in adults and the head and neck in children. We know of only three case reports of intraoral locations without tongue involvement. Here, we describe the first case of an alveolar soft-part sarcoma of the cheek which presented in a patient over 30 years old and had an extremely rapid and eventually fatal evolution. We have also reviewed hypotheses about its aetiology.


Subject(s)
Cheek/pathology , Facial Neoplasms/diagnosis , Sarcoma, Alveolar Soft Part/diagnosis , Biopsy , Facial Muscles/pathology , Fatal Outcome , Female , Follow-Up Studies , Humans , Middle Aged , Neoplasm Invasiveness , Neoplasm Staging , Pharyngeal Neoplasms/pathology , Sarcoma, Alveolar Soft Part/pathology , Sarcoma, Alveolar Soft Part/secondary , Tomography, X-Ray Computed , Tonsillar Neoplasms/pathology
20.
Development ; 128(20): 4011-20, 2001 Oct.
Article in English | MEDLINE | ID: mdl-11641224

ABSTRACT

In vertebrates the neural tube, like most of the embryonic organs, shows discreet areas of programmed cell death at several stages during development. In the chick embryo, cell death is dramatically increased in the developing nervous system and other tissues when the midline cells, notochord and floor plate, are prevented from forming by excision of the axial-paraxial hinge (APH), i.e. caudal Hensen's node and rostral primitive streak, at the 6-somite stage ( Charrier, J. B., Teillet, M.-A., Lapointe, F. and Le Douarin, N. M. (1999). Development 126, 4771-4783). In this paper we demonstrate that one day after APH excision, when dramatic apoptosis is already present in the neural tube, the latter can be rescued from death by grafting a notochord or a floor plate fragment in its vicinity. The neural tube can also be recovered by transplanting it into a stage-matched chick embryo having one of these structures. In addition, cells engineered to produce Sonic hedgehog protein (SHH) can mimic the effect of the notochord and floor plate cells in in situ grafts and transplantation experiments. SHH can thus counteract a built-in cell death program and thereby contribute to organ morphogenesis, in particular in the central nervous system.


Subject(s)
Apoptosis/physiology , Nervous System/embryology , Trans-Activators/physiology , Animals , Chick Embryo , Coturnix , Hedgehog Proteins , In Situ Hybridization , Nervous System/cytology , Notochord/transplantation , Somites/cytology , Trans-Activators/genetics
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