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Biomedical subjects

E Arslan

Publications and source records attributed to E Arslan.

At least 19 recordsLinked to original sources
PubMed2006

Cochlear microphonic potential recorded by transtympanic electrocochleography in normally-hearing and hearing-impaired ears.

The cochlear microphonic is a receptor potential believed to be generated primarily by outer hair cells. Its detection in surface recordings has been considered a distinctive sign of outer hair cell integrity in patients with auditory neuropathy. This report focuses on the results of an analysis performed on cochlear microphonic recorded by transtympanic electrocochleography in response to clicks in 502 subjects with normal hearing threshold or various degrees of hearing impairment, and in 20 patients with auditory neuropathy. Cochlear microphonics recorded in normally-hearing and hearing-impaired ears showed amplitudes decreasing by the elevation of compound action potential Cochlear microphonic responses were clearly detected in ears with profound hearing loss. After separating recordings according to the presence or absence of central nervous system pathology (CNS+ and CNS-, respectively), cochlear microphonic amplitude was significantly higher in CNS+ than in CNS- subjects with normally-hearing ears and at 70 dB nHL compound action potential threshold. Cochlear microphonic responses were detected in all auditory neuropathy patients, with similar amplitudes and thresholds to those calculated for normally-hearing CNS- subjects. Cochlear microphonic duration was significantly higher in auditory neuropathy and normally-hearing CNS+ patients compared to CNS- subjects. Our results show that: 1. cochlear microphonic detection is not a distinctive feature of auditory neuropathy; 2. CNS+ subjects showed enhancement in cochlear microphonic amplitude and duration, possibly due to efferent system dysfunction; 3. long-lasting, high frequency cochlear microphonics with amplitudes comparable to those obtained from CNS- ears were found in auditory neuropathy patients. This could result from a variable combination of afferent compartment lesion, efferent system dysfacilitation and loss of outer hair cells.

Adolescent↗
PubMed2004

Method for the deconvolution of auditory steady-state responses.

The potential evoked by a 'train' of N equally spaced auditory clicks, with an inter-click period shorter than the duration of the response to an isolated click, is said to be a steady-state response (SSR). Extracting the individual responses evoked by the clicks of the train during steady state can be key to understanding of the neurophysiological mechanisms underlying SSR generation. In the literature, this task has been dealt with only under the (unwarranted) assumption that the response of the system does not vary during the presentation of the clicks, i.e. no neurophysiological adaptation is present. In this work, a new, non-parametric algorithm is proposed that, relaxing the time-invariance hypothesis, allows the extraction from the SSR of the N waveforms individually evoked by the N clicks of the train. The performance of the approach is evaluated on simulated SSRs and on real data recorded from the temporal cortex of awake rats. Results show that the method is able to detect and assess possible adaptation of the neurophysiological system in the generation of SSRs.

Acoustic Stimulation↗
PubMed2004

Long-term effectiveness of steroid injections and splinting in mild and moderate carpal tunnel syndrome.

To evaluate the long-term efficacy of non-surgical treatment methods for mild and moderate carpal tunnel syndrome, 120 patients with clinical symptoms and electrophysiologic evidence were included in a prospective, randomized and blinded trial: 60 patients were instructed to wear splints every night, 30 received injections of betamethasone 4 cm proximal to the carpal tunnel, and 30 received injections distal to the carpal tunnel. After approximately 1 year (mean, 11 months; range, 9-14), 108 patients were available for final evaluation. We assessed clinical symptom severity and performed detailed electrophysiologic examinations before and after treatment. Splinting provided symptomatic relief and improved sensory and motor nerve conduction velocities at the long-term follow-up when the splints were worn almost every night. Proximal and distal injections of steroids were ineffective on the basis of both clinical symptoms and electrophysiologic findings.

Adult↗
PubMed2003

Multifocal intradiploic cavernous hemangioma of the skull associated with nasal osteoma.

OBJECTIVE: To present a 42-year-old female patient with multifocal cavernous hemangioma of the skull associated with nasal osteoma. DESIGN: A case report. INTERVENTION METHODS: X-rays, computerized tomography, magnetic resonance imaging, and histopathology were used to achieve the diagnosis of this rare entity. The multiple cavernous hemangiomas were resected en-bloc and a curettage biopsy was obtained from the nasal osteoma. RESULTS: The patient healed well after the operation. No recurrences of the cavernous hemangiomas were observed after one-year follow-up. CONCLUSION: Multifocal cavernous hemangiomas are rare benign lesions of the calvarium, arising from the intrinsic vasculature of the bone. Although they are benign, radiological findings are not always characteristic and their multiple presentation may easily make surgeons consider the other malignancies of the skull in the differential diagnosis. Histopathologic confirmation of the tumor is the definitive method for diagnosis. The treatment of choice is early en bloc resection of the tumour where it is possible.

Adult↗
PubMed2000

The symbiotically essential cbb(3)-type oxidase of Bradyrhizobium japonicum is a proton pump.

Purified cbb(3)-type oxidase of Bradyrhizobium japonicum was reconstituted into phospholipid vesicles. Tight vesicles were obtained as shown by the disturbance of deltapH with CCCP and the membrane potential with valinomycin, which led to a six-fold increase in cytochrome c oxidase activity. The vesicles were thus suitable for proton translocation experiments. In the presence of valinomycin, a pulse with reduced cytochrome c caused an acidification with a subsequent alkalinization, whereas the same pulse caused only an alkalinization in the presence of valinomycin plus CCCP. We conclude that the cbb(3)-type oxidase of B. japonicum is a proton pump.

Bacterial Proteins↗
PubMed2000

The relationship between tumor necrosis factor (TNF)-alpha and survival following granulocyte-colony stimulating factor (G-CSF) administration in burn sepsis.

Blood levels of tumor necrosis factor (TNF)-alpha were determined in 78 patients with burn sepsis. Of these patients, 51 were managed with additional administration of granulocyte colony-stimulating factor (G-CSF) in addition to routine treatment procedures (group A), while 27 received only routine treatment (group B). G-CSF was administrated for at least nine and at most 14 days; doses were gradually decreased in each 3 day period. On the 1st, 4th, 7th, 10th and 15th days, blood levels of TNF-alpha were determined. We sought to determine whether TNF alpha levels had a prognostic value in the management of burn induced sepsis that was treated with G-CSF. In our study, patients with gradually decreasing TNF-alpha levels in the second 3 day period, were strong candidates for survival, because TNF-alpha levels decreased little in nonsurvivors but decreased greatly in survivors. The survival rate was 42/51 (82.3%) in group A and 9/27 (33.3%) in group B. In conclusion, G-CSF had positive effects on survival, and TNF-alpha was a predictor of prognosis in burn-induced sepsis.

Adolescent↗
PubMed2000

Compound action potential and cochlear microphonic extracted from electrocochleographic responses to condensation or rarefaction clicks.

In electrocochleography (ECochG) compound action potential (CAP) and summation potential (SP) are usually separated from the cochlear microphonic (CM) by the CM cancellation technique consisting in averaging the responses evoked by rarefaction and condensation clicks. With the aim of analysing the ECochG responses evoked by monophasic clicks, we developed a numerical method based on the theory of optimal filtering, which makes no assumptions about the unknown potentials. The application of the filtering technique to the ECochG recordings obtained from 6 normally hearing children and 10 children with cochlear hearing loss allowed us to perform CAP extraction in cases where CM was not cancelled by the conventional method. Differences in SP amplitude and polarity were found between rarefaction and condensation click-evoked responses in cochlear hearing losses.

Acoustic Stimulation↗
PubMed1999

Global problem of drug-induced hearing loss.

Clinically used drugs and chemical agents may potentially cause adverse effects to the human auditory and vestibular systems. Many of them, such as aminoglycosides and cisplatin, can play a critical role in the treatment of serious or life-threatening diseases; others, like loop diuretics or salycilates, offer such important therapeutical effects compared to the ototoxic side effects that the ototoxicity risk can be considered to be of minor importance. The problem of ototoxic side effects is more acute in developing countries, where highly effective and low-cost drugs are more easily prescribed without adequate monitoring. Medical awareness of doses, forms of administration, populations at risk, and possible synergism is necessary in order to develop appropriate care in the prescription of drugs with ototoxic side effects. Relatively recent issues such as risk-benefit analysis, patient-informed consent, and quality-of-life considerations, particularly when life expectancy can be low, are also to be considered. At present, a uniform method of monitoring for all potentially ototoxic therapeutics does not seem reasonable or practical. It is recommended, however, that individual auditory function be noted for a particular drug being employed. Protocols and exams should be easy, quick, sensitive, reliable, and as objective as possible. Benefits of audiological monitoring include the opportunity to change the patient's treatment course, improvement of patient and family awareness of the impact of hearing impairment, and timely prescription of amplification devices. Finally, particular attention should be paid to high-risk populations such as neonatal intensive care unit patients.

Aminoglycosides↗
PubMed1999

[Acoustic distortion products otoacoustic emissions (DPOAE) in neonatal screening].

The purpose of the work was to determine the feasibility of direct nursery DPOAE testing in a universal hearing screening, evaluate the results and calculate the reliability of this test vs. Auditory Brainstem Responses (ABR). To this purpose DPOAE (sweep and I/O test) were performed on 500 children born between January and August 1996 at the Civil Hospital of Mestre, Italy. All the children were examined in the nursery, no matter what the risk factors or specific motivations. Besides determining whether the examination could be performed, its specificity and sensitivity, the time required and any variation depending on the day of testing were also evaluated. In a high percentage of cases (11.2%) it proved impossible to perform the test. In addition, when compared to ABR, the percentage of false positives was rather high (16.2%) and specificity was 84%. As conceived, the test requires 6'09" per ear. Comparison of the differences in results according to day of execution did not appear significant although there was a lower percentage of false positive after the third day of life. DPOAE can be measured in the nursery. The high number of false positives and the frequent need to repeat the measurements, however, increase the amount of time required for this test, thus voiding any time savings over an ABR screening: a test which is rather lengthy by provides a high degree of specificity.

Acoustic Stimulation↗
PubMed1999

Cx26 deafness: mutation analysis and clinical variability.

Mutations in the gap junction protein connexin 26 (Cx26) gene (GJB2) seem to account for many cases of congenital sensorineural hearing impairment, the reported prevalence being 34-50% in autosomal recessive cases and 10-37% in sporadic cases. The hearing impairment in these patients has been described as severe or profound. We have studied 53 unrelated subjects with congenital non-syndromic sensorineural hearing impairment in order to evaluate the prevalence and type of Cx26 mutations and establish better genotype-phenotype correlation. Mutations in the Cx26 gene were found in 53% of the subjects tested, 35.3% of the autosomal recessive and 60% of the sporadic cases in our series. Three new mutations were identified. The hearing deficit varied from mild to profound even in 35delG homozygotes within the same family. No evidence of progression of the impairment was found. Alterations of the Cx26 gene account for a large proportion of cases of congenital non-syndromic sensorineural deafness, so it seems appropriate to extend the molecular analysis even to subjects with mild or moderate prelingual hearing impairment of unknown cause.

Adolescent↗
PubMed1998

Overproduction of the Bradyrhizobium japonicum c-type cytochrome subunits of the cbb3 oxidase in Escherichia coli.

We report on a system to improve expression of mature c-type cytochromes in Escherichia coli. It is based on the use of plasmid pEC86 that expresses the E. coli cytochrome c maturation genes ccmABCDEFGH constitutively, whereby the production of both endogenous and foreign c-type cytochromes was increased substantially. The periplasmic soluble domains of the c-type cytochrome subunits FixO and FixP of the Bradyrhizobium japonicum cbb3 oxidase could be expressed in E. coli only when pEC86 was provided in a degP-deficient strain. This shows that a stimulation of heme attachment by the Ccm maturase system combined with the diminished proteolytic activity in the periplasm can increase c-type cytochrome yields.

Bradyrhizobium↗
PubMed1998

How replacements of the 12 conserved histidines of subunit I affect assembly, cofactor binding, and enzymatic activity of the Bradyrhizobium japonicum cbb3-type oxidase.

Alignments of the amino acid sequences of subunit I (FixN or CcoN) of the cbb3-type oxidases show 12 conserved histidines. Six of them are diagnostic of heme-copper oxidases and are thought to bind the following cofactors: the low spin heme B and the binuclear high spin heme B-CuB center. The other six are FixN(CcoN)-specific and their function is unknown. To analyze the contribution of these 12 invariant histidines of FixN in cofactor binding and function of the Bradyrhizobium japonicum cbb3-type oxidase, they were substituted by valine or alanine by site-directed mutagenesis. The H131A mutant enzyme had already been reported previously to be defective in oxidase assembly and function (Zufferey, R., Th¿ny-Meyer, L., and Hennecke, H. (1996) FEBS Lett. 394, 349-352). Four of the remaining histidines were not essential for activity or assembly (positions 226, 246, 333, and 457); by contrast, histidines 331, 410, and 418 were required both for activity and stability of the enzyme. The last group of mutant enzymes, H420A, H280A, H330A, and H316V, were assembled but not functional. To purify the latter mutant proteins and the wild-type enzyme, a six-histidine tag was added to the C terminus of subunit I. The His6-tagged cbb3-oxidase complexes were purified 20-fold by a three-step purification protocol. With the exception of the H420A mutant oxidase, the mutant enzymes H280A, H316V, and H331A contained normal amounts of copper and heme B, and they displayed similar visible light spectroscopic characteristics like the wild-type His6-tagged enzyme. The His6-tagged H420A mutant oxidase differed from the His6-tagged wild-type protein by showing altered visible light spectroscopic characteristics. No stable mutant oxidase lacking copper or heme B was obtained. This strongly suggests that copper and heme B incorporations in subunit I are prerequisites for assembly of the enzyme.

Amino Acid Sequence↗
PubMed1998

Audiological management of noise induced hearing loss.

Noise-induced hearing loss (NIHL) has no specific of exclusive audiological signs. The disorder is identified on the strength of a high probability conclusion and as a result of an exclusion process. Because of frequent legal purposes, audiometrical data measured and analyzed have furthermore to be as accurate and reliable as possible. The paper outlines the whole procedure involved in the audiological assessment of noise-induced hearing loss considering different stages for: suspicion and identification, hearing threshold measurement, etiological and differential diagnosis, apportionment.

Acoustic Impedance Tests↗
PubMed1997

Hearing threshold assessment with auditory brainstem response (ABR) and ElectroCochleoGraphy (ECochG) in uncooperative children.

Two-hundred-and-sixty uncooperative children (442 ears) performed auditory brainstem response (ABR) and Electrocochleography (ECochG) in the same diagnostic session under general anaesthesia, and the results obtained with the two different methods were compared. A difference > or = 20 dB between the two methods was found in 134 ears (30.3%). The presence of middle ear effusion and symptoms of a possible central nervous system pathology were considered in order to verify the evidence of a correlation between the difference in ABR-ECochG results and these clinical parameters. The presence of middle ear effusion was not significantly correlated with differences > or = 20 dB (p = 0.1347). On the contrary, the presence of symptoms indicative of a possible central nervous system (CNS) involvement was significantly correlated with differences > or = 20 dB (p = 0.0000). ABR has to be considered the first choice in hearing assessment strategy, either for screening or diagnosis. However, the diagnosis of hearing loss only on the basis of the presence or absence of wave V requires some care in case of suspected central auditory pathway lesions. In these cases, ECochG may be the only reliable diagnostic tool for hearing assessment in uncooperative subjects.

Adolescent↗
PubMed1997

Cochlear implantation in a bilateral Mondini dysplasia.

We report the speech perception progress and programming procedures of a case of congenital profound deafness and bilateral Mondini dysplasia implanted with a Nucleus 20 + 2 cochlear implant at the age of six. Unclear relations between electrodes array and cochlear partition made implant programming difficult and non-standard procedures were set. Cochlear implantation may give excellent rehabilitative results also in cochleae with malformation.

Child↗
PubMed1996

Evaluation of noise in the neonatal intensive care unit.

This study evaluated the noise level inside the incubators in a neonatal intensive care unit and identified its sources in order to attempt to reduce it. Although noise is not a proven risk factor as far as the sensory integrity of newborns is concerned, it is certainly an important cause of stress to them and a source of serious and dangerous changes in their behavioral and physiologic states. Noise recorded inside the incubators had two components. The first was background noise from the incubator motors, which varied from 74.2 to 79.9 dB, and was similar to environmental noise. The second source was impulsive events beyond 80 dB. These events were the result of voluntary and involuntary contact with the incubators' Plexiglas surface or to the abrupt opening and closing of their access ports. Considering its decibel levels and frequency, this latter component is undoubtedly an important source of stress to newborns. Moreover, these data reveal the need to train health care personnel on how to reduce such noise by taking more care in the handling of infants.

Environmental Exposure↗
PubMed1996

Hearing aid systems in undeveloped, developed and industrialized countries.

The problems related with the hearing loss prevalence and deafness rehabilitation in Developing (D) countries are so complex that only basic needs and some suggestions are discussed in this paper. In fact for D countries the main demographic and social indi reveal the enormous gravity of the health situation and so the availability of a hearing aid delivery system is often considered less urgent and secondary to the basic unmet needs of the population. Nevertheless we think this concept may be applied to the adult, but for the child with a preverbal deafness it must deserve immediate attention in order to prevent a very serious handicap limiting all his life. Schematically the three types of handicaps developed by a child with a preverbal hearing loss are presented and discussed. The essential assumption, however, for any hearing aid program in D countries is the creation in loco of competent personnel for the prescription, for fitting and checking the aids. If D countries are to achieve this objective, industrialized countries must begin to transfer technology and training to develop pilote centers.

Africa↗