Transcriptionally dynamic progenitor populations organised around a stable niche drive axial patterning.

The elongating mouse anteroposterior axis is supplied by progenitors with distinct tissue fates. It is not known whether these progenitors confer anteroposterior pattern to the embryo. We have analysed the progenitor population transcriptomes in the mouse primitive streak and tail bud throughout axial elongation. Transcriptomic signatures distinguish three known progenitor types (neuromesodermal, lateral/paraxial mesoderm and notochord progenitors; NMPs, LPMPs and NotoPs). Both NMP and LPMP transcriptomes change extensively over time. In particular, NMPs upregulate Wnt, Fgf and Notch signalling components, and many Hox genes as progenitors transit from production of the trunk to the tail and expand in number. In contrast, the transcriptome of NotoPs is stable throughout axial elongation and they are required for normal axis elongation. These results suggest that NotoPs act as a progenitor niche whereas anteroposterior patterning originates within NMPs and LPMPs.

Intrinsic factors and the embryonic environment influence the formation of extragonadal teratomas during gestation.

BACKGROUND: Pluripotent cells are present in early embryos until the levels of the pluripotency regulator Oct4 drop at the beginning of somitogenesis. Elevating Oct4 levels in explanted post-pluripotent cells in vitro restores their pluripotency. Cultured pluripotent cells can participate in normal development when introduced into host embryos up to the end of gastrulation. In contrast, pluripotent cells efficiently seed malignant teratocarcinomas in adult animals. In humans, extragonadal teratomas and teratocarcinomas are most frequently found in the sacrococcygeal region of neonates, suggesting that these tumours originate from cells in the posterior of the embryo that either reactivate or fail to switch off their pluripotent status. However, experimental models for the persistence or reactivation of pluripotency during embryonic development are lacking. METHODS: We manually injected embryonic stem cells into conceptuses at E9.5 to test whether the presence of pluripotent cells at this stage correlates with teratocarcinoma formation. We then examined the effects of reactivating embryonic Oct4 expression ubiquitously or in combination with Nanog within the primitive streak (PS)/tail bud (TB) using a transgenic mouse line and embryo chimeras carrying a PS/TB-specific heterologous gene expression cassette respectively. RESULTS: Here, we show that pluripotent cells seed teratomas in post-gastrulation embryos. However, at these stages, induced ubiquitous expression of Oct4 does not lead to restoration of pluripotency (indicated by Nanog expression) and tumour formation in utero, but instead causes a severe phenotype in the extending anteroposterior axis. Use of a more restricted T(Bra) promoter transgenic system enabling inducible ectopic expression of Oct4 and Nanog specifically in the posteriorly-located primitive streak (PS) and tail bud (TB) led to similar axial malformations to those induced by Oct4 alone. These cells underwent induction of pluripotency marker expression in Epiblast Stem Cell (EpiSC) explants derived from somitogenesis-stage embryos, but no teratocarcinoma formation was observed in vivo. CONCLUSIONS: Our findings show that although pluripotent cells with teratocarcinogenic potential can be produced in vitro by the overexpression of pluripotency regulators in explanted somitogenesis-stage somatic cells, the in vivo induction of these genes does not yield tumours. This suggests a restrictive regulatory role of the embryonic microenvironment in the induction of pluripotency.

The developmental dismantling of pluripotency is reversed by ectopic Oct4 expression.

The transcription factors Nanog and Oct4 regulate pluripotency in the pre-implantation epiblast and in derivative embryonic stem cells. During post-implantation development, the precise timing and mechanism of the loss of pluripotency is unknown. Here, we show that in the mouse, pluripotency is extinguished at the onset of somitogenesis, coincident with reduced expression and chromatin accessibility of Oct4 and Nanog regulatory regions. Prior to somitogenesis expression of both Nanog and Oct4 is regionalized. We show that pluripotency tracks the in vivo level of Oct4 and not Nanog by assessing the ability to reactivate or maintain Nanog expression in cell culture. Enforced Oct4 expression in somitogenesis-stage tissue provokes rapid reopening of Oct4 and Nanog chromatin, Nanog re-expression and resuscitates moribund pluripotency. Our data suggest that decreasing Oct4 expression is converted to a sudden drop in competence to maintain pluripotency gene regulatory network activity that is subsequently stabilized by epigenetic locks.

Enhanced podocalyxin expression alters the structure of podocyte basal surface.

Glomerular basement membrane (GBM) and podocalyxin are essential for podocyte morphology. We provide evidence of functional interconnections between basement membrane components (collagen IV and laminin), the expression of podocalyxin and the morphology of human glomerular epithelial cells (podocytes). We demonstrated that GBM and laminin, but not collagen IV, up-regulated the expression of podocalyxin. Scanning electron microscopy revealed that laminin induced a modified morphology of podocytes with process formation, which was more extensive in the presence of GBM. Under high magnification, podocytes appeared ruffled. Using transmission electron microscopy we observed that raised areas occurred in the basal cell surface. Furthermore, the presence of anti-podocalyxin antibody increased the extent of adhesion and spreading of podocytes to both collagen IV and laminin, thus podocalyxin apparently inhibits cell-matrix interactions. We also performed adhesion and spreading assays on podocytes grown under increased glucose concentration (25 mM). Under these conditions, the expression of podocalyxin was almost totally suppressed. The cells adhered and spread to basement membrane components but there was no increase in the extent of adhesion and spreading in the presence of anti-podocalyxin antibody, or ruffling of the cell edges. Additionally, in podocytes expressing podocalyxin, the presence of anti-podocalyxin antibody partially reversed the inhibition of adhesion to collagen IV provoked by anti-beta1 integrin antibody, thus podocalyxin should compete with beta1-related cell adhesion. We suggest that the observed podocalyxin-mediated inhibition of binding to the matrix could be in part responsible for the specialized conformation of the basal surface of podocytes.

Detection of pseudohypacusis: a prospective, randomized study of the use of otoacoustic emissions.

OBJECTIVES: This study was designed to evaluate the effectiveness of transient otoacoustic emissions in an audiological protocol used in the evaluation of patients suspicious of pseudohypacusis. DESIGN: This was a prospective study of 72 adult patients suspicious of pseudohypacusis on the grounds of case history and inconsistent audiometric results. The subjects were randomly assigned to a treatment group or control group. The treatment group consisted of 42 patients who underwent a four-stage protocol that included (1) standard speech and pure-tone audiometry, (2) transiently evoked otoacoustic emissions (TEOAEs) and tympanometry, (3) repeat modified pure-tone audiometry, and (4) auditory brain stem response (ABR) audiometry. The control group consisted of 30 patients, who underwent an identical protocol except that Stage 2 (TEOAEs and tympanometry) was omitted. The main outcome measure was the mean exaggeration level defined as the difference in mean pure tone average (PTA) between the initial and the repeat session (mean PTAinitial minus mean PTArepeat). RESULTS: The mean PTA (average threshold at 1, 2, 3, and 4 kHz) on repeat audiometry was significantly better than the mean PTA obtained on the initial evaluation for each group. However, the mean exaggeration level was significantly greater for the treatment group (35.2 dB HL) than for the control group (11.0 dB HL). In addition, there was no significant difference between the mean PTArepeat (32.7 dB HL) and the mean click-evoked ABR threshold (31.6 dB nHL) for the treatment group whereas the mean PTArepeat (52.9 dB HL) was significantly poorer than the click evoked ABR threshold (29.2 dB nHL) for the control group. CONCLUSIONS: The inclusion of TEOAEs and tympanometry in an audiological protocol used in the evaluation of patients suspicious of pseudohypacusis resulted in a significantly greater threshold improvement on repeat modified pure-tone audiometry when compared to the improvement observed for a control group in which these tests were not performed.

Otoacoustic emissions in patients with hypotension.

The aim of this study was to investigate the relation between hypotension and slowly developing hearing impairment, using otoacoustic emissions. A group of 42 patients was examined, with diastolic blood pressure < or = 60 mmHg and systolic blood pressure < or = 105 mmHg. The subjects underwent biochemical, cardiological, ENT and audiological examinations. Distortion product otoacoustic emissions (DPOAE) were recorded in the format of DP-gram. The results were compared to the data of 30 normal persons of similar age and sex, examined at the same laboratory. Audiometric results showed that 18 patients had mild or moderate symmetrical hearing loss in one or more frequencies, mainly in the lower frequency range. DPOAE of the patients had reduced amplitude as compared to controls or were even absent, in one or more frequencies. It may be concluded that a hypotensive condition could be a possible factor in the origin of cochlear damage and DPOAE may be useful in monitoring hypotensive patients.

Newborn hearing screening resources on the Internet.

Starting as a small military and academic network, the Internet has gradually evolved into a worldwide web, which connects most local networks as well as millions of personal computers from individual users. It is of interest to the medical practitioner, that ever more biomedical resources are becoming available on-line to assist in clinical medicine, research and education. In this paper a detailed list of the World Wide Web sites accessible through the Internet is provided, in which data about newborn hearing screening may be found. Web resources of medical equipment and suppliers and sites including otoacoustic emissions topics, are presented as well. This review is intended to present the wealth of the accessible information on the Internet and to promote further presentation on the web of any available hearing screening data from hospitals and Audiology Departments in which such programs are implemented.

Internet resources available to otolaryngologists.

During recent years, the Internet has evolved into the largest computer network in the world, allowing access to vast amounts of information and services. Medical information is increasingly available to both patients and professionals, and ever more biomedical resources are becoming available on-line to assist in research, clinical medicine, and education. The Internet has always provided useful resources to otolaryngologists, implemented at various academic departments and national organizations or by specialists or specific medical web sites offering technical, scientific, and biomedical information. The purpose of this article is to provide as complete a list as possible of the World Wide Web sites accessible through the Internet that are of interest to otolaryngologists. It summarizes different types of resources available, including educational material, audiology sites, outcomes research, discussion lists, research laboratories, publications, medical libraries, news and medical conferences, organizations, academic departments, otolaryngological and medical resources, medical and surgical equipment and suppliers, and miscellaneous other sites of interest to otolaryngologists. This review is intended to present the wealth of the accessible information on the Internet and to promote the use of the network to otolaryngologists who do not have extensive experience in computers or telecommunications.

Cochlear dysfunction in patients with mitochondrial myopathy.

The present study investigates cochlear function in a group of 11 patients suffering from mitochondrial myopathy with normal or near normal audiometric pure tone thresholds, in most of whom diagnosis was histologically confirmed. A complete ENT, neurologic and audiological work-up, including transiently evoked otoacoustic emissions, was performed in all patients in order to estimate cochlear function. Compared to control subjects, most patients had absent otoacoustic emissions (OAE) in spite of normal hearing, indicating cochlear dysfunction. These findings suggest that subclinical involvement of the cochlea is quite common in patients with mitochondrial myopathy. Damage of the cochlea can be explained on the grounds of its increased metabolic rate, resulting in failure of the stria vascularis and the outer hair cells. Otoacoustic emissions might provide a useful tool in the clinical work-up and follow-up of these patients.

Occurrence of semicircular canal involvement in benign paroxysmal positional vertigo.

OBJECTIVES: To study the occurrence of each variant of benign paroxysmal positional vertigo (BPVV) and to present some specific clinical features and the results of their treatment by appropriate repositioning maneuvers. STUDY DESIGN: A retrospective review of the records of patients with BPPV. SETTING: Neurotology clinic of the ear, nose, and throat department of a general hospital. PATIENTS: One hundred twenty-two patients were included in the study, 54 male and 68 female, mean ages 61.8 and 59.6 years, respectively, ranging in age from 25 years to 86 years and with symptoms lasting for an average of 124 days. The diagnosis of each type of BPPV was based on the history of the patients and on the positive results of the appropriate provoking maneuver. METHODS: From all the patients, a comprehensive history was obtained, followed by clinical examination of the ears, nose, and throat and a complete audiologic and neurotologic examination, including electronystagmography. All patients were treated with an appropriate repositioning maneuver, depending on the type of BPPV. RESULTS: Of 122 patients, 110 had posterior canal involvement, 10 had horizontal canal involvement, and only 2 had the anterior canal variant. The canalith repositioning procedure was immediately successful in 106 patients and in 8 more patients proved successful after its repetition in a second session, resulting in a total success rate of 93.4%. CONCLUSIONS: All the BPPV variants shared the same clinical and demographic characteristics and responded equally well to treatment. However, differential diagnosis was necessary to apply the appropriate canalith repositioning procedure. Although data from clinical and histologic studies do not fully account for the observed relative occurrence of each variant of BPPV, a satisfactory explanation may be provided by the anatomic location of each semicircular canal and additionally by self-treatment of most cases of the horizontal and the anterior canal variety.

Rhinolithiasis: an unusual cause of nasal obstruction.

Rhinoliths are foreign bodies of the nose, which may be encountered during the course of a routine examination. If undetected for a long time, they may grow large enough to cause symptoms of nasal obstruction, mimicking sinusitis. We report four patients with rhinoliths presenting with diverse clinical findings. Removal was easy and uneventful in all cases.

Audiological assessment in Ramsay Hunt syndrome.

Ramsay Hunt syndrome is known to cause symptoms and signs of vestibulocochlear dysfunction, including sensorineural hearing loss. The present study investigates the audiological features of a group of 15 patients with this syndrome. A complete otolaryngological, neurologic, and audiological workup was performed in every patient, including auditory brain stem response measurements and recording of transiently evoked otoacoustic emissions. In most patients, some degree of hearing loss was evident, and abnormal latencies and interpeak latencies of the auditory brain stem response, or even absence of the waves, were observed. Transiently evoked otoacoustic emissions were present in only 6 cases, and caloric tests showed unilateral weakness in the majority of the patients. In all of the performed tests, abnormalities were present only on the affected side. The audiological data suggested cochlear or retrocochlear involvement or involvement at more than one site along the auditory pathway.

Rhinology resources on the Internet.

During recent years medical information through Internet is increasingly available to both patients and professionals and ever more biomedical resources become available on line to assist in clinical medicine, education and research. The purpose of this article is to present a detailed list of all the worldwide web sites of rhinology that are accessible through the Internet.