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Biomedical subjects

S Freeman

Publications and source records attributed to S Freeman.

242 records · Page 14Linked to original sources
PubMedDate not supplied

The pathway enabling external sounds to reach and excite the fetal inner ear.

The human fetus in utero is able to respond to sounds in the amniotic fluid enveloping the fetus after about 20 weeks gestation. The pathway by which sound reaches and activates the fetal inner ear is not entirely known. It has been suggested that in this total fluid environment, the tympanic membrane and the round window membrane become 'transparent' to the sound field, enabling the sounds to reach the inner ear directly through the tympanic membrane and the round window membrane. It is also possible that sounds reach the inner ear by means of tympanic membrane--ossicular chain--stapes footplate conduction (as in normal air conduction). There is also evidence that sounds reach the fetal inner ear by bone conduction. Several animal and human models of the fetus in utero were studied here in order to investigate the pathway enabling sounds to reach and activate the fetal inner ear. This included studying the auditory responses to sound stimuli of animals and humans under water. It was clearly shown in all the models that the dominant mechanism was bone conduction, with little if any contribution from the external and middle ears. Based on earlier experiments on the mechanism and pathway of bone conduction, the results of this study lead to the suggestion that the skull bone vibrations induced by the sound field in the amniotic fluid enveloping the fetus probably give rise to a sound field within the fetal cranial cavity (brain and CSF) which reaches the fetal inner ear through fluid communication channels connecting the cranial cavity and the inner ear.

Animals↗
PubMedDate not supplied

The neonate has a temporary conductive hearing loss due to fluid in the middle ear.

Postnatal functional changes in the activity of the ear and auditory pathway in neonatal guinea pigs [from day of birth (postnatal day, PND = 0), PNDs 1-4, 7 and then weekly up to 7 weeks] were studied as a model of maturation of hearing in human neonates. On the day of birth there were signs of a conductive hearing loss: negative middle ear pressure, auditory nerve brainstem evoked response (ABR) threshold elevation, ABR wave 1 latency prolongation and low amplitude otoacoustic emissions. The conductive hearing loss is probably a result of the (amniotic) fluid found in the neonatal middle-ear cavity. Over the next PNDs, this conductive hearing loss was resolved. In order to confirm this neonatal conductive hearing loss and its resolution, saline was instilled into the middle ear of guinea pigs. This induced signs of a conductive hearing loss similar to those seen in the neonatal guinea pigs which disappeared with clearance of this fluid. Therefore it may be concluded that most of the changes in auditory function seen over the first PNDs are due to absorption of amniotic fluid from the middle-ear cavity.

Acoustic Impedance Tests↗
PubMedDate not supplied

The importance of thyroid hormone for auditory development in the fetus and neonate.

It seems that many auditory maturational events are regulated by thyroid hormone since elevation in thyroid hormone level always precedes the onset of hearing in the fetus-neonate; low thyroid activity in the developing human fetus or rat neonate leads to hearing loss; earlier, elevated thyroid levels in rat neonate lead to earlier onset of hearing. The hormone, bound to its receptors in the nucleus, acts as a transcription factor activating genes which lead to the synthesis of several proteins and enzymes involved in the structural and functional development of many tissues (e.g. brain, heart, kidney, skeletal muscle) including the ear. Several types of congenital hearing loss of unexplained etiology may be due to abnormalities in one or more stages of this gene cascade since several types of congenital hearing loss have been shown to involve defects in genes related to these events.

Animals↗
PubMedDate not supplied

Transient evoked otoacoustic emissions in newborns in the first 48 hours after birth.

Newborns are often discharged from hospital at the age of about 48 hours. At this age, transient evoked otoacoustic emissions (TEOAEs) are not necessarily recordable in all healthy newborns. In order to determine the factors which would enable the successful recording of TEOAEs before discharge to facilitate screening for hearing, 65 fullterm newborns under 48 hours of age were tested, the youngest being 10 hours old. The ears of those neonates in whom TEOAEs could not be obtained (N = 7 neonates bilaterally, 6 unilaterally) were examined otoscopically, cleaned of vernix and retested for TEOAEs. We were thus able to record in at least one ear in all neonates tested, if the ears were clean, if they were asleep and if the testing room was quiet.

Acoustic Stimulation↗
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Transient evoked otoacoustic emissions in laboratory animals.

Transient evoked otoacoustic emissions (TEOAEs) are much used clinically. However, it has been difficult to record them in small laboratory animals, and experimental manipulations designed to determine the generation mechanisms of this type of emission could not be performed. After refining the technique, based on the use of short clicks and a short amplifier gain suppression period, TEOAEs were recorded using the same instrumentation and techniques in rabbits, Psammomys obesus (fat sand rats), mice, rats and guinea pigs. Distortion product emissions were also recorded. The responses in each species differed with respect to threshold, magnitude, frequency spectrum and duration (endpoint). The ability to record TEOAEs routinely in laboratory animals should now allow for further experimentation on the mechanisms of their generation, on the cochlear amplifier in general and on the comparison of TEOAEs with distortion product emissions in individual species and animals.

Acoustic Stimulation↗
PubMedDate not supplied

Cushing's syndrome secondary to olfactory neuroblastoma.

A case of olfactory neuroblastoma in a 36-year-old woman who presented with florid Cushing's syndrome is reported. A nasal polyp, which proved to be an olfactory neuroblastoma, was resected. The procedure was followed by complete remission from the endocrinologic abnormalities. Postoperatively, the patient was well for 5 years until recurrence of both Cushing's syndrome and the nasal polyp was noted. Following combined transnasal-transcranial resection of the tumor, which extended into the anterior cranial fossa, the patient again experienced complete remission of Cushing's syndrome. Immunohistochemistry showed the tumor to be positive for neuron-specific enolase, synaptophysin, chromogranin, adrenocorticotropic hormone, beta-endorphin, and S-100 protein. Electron microscopy revealed neuritic processes containing microtubules and neurosecretory granules. This is the first reported case of Cushing's syndrome secondary to olfactory neuroblastoma.

Adult↗
PubMedDate not supplied

Measuring services: a district nursing dependency tool.

The government has highlighted the importance of reducing inequalities in health and providing an equal and high quality service to all patients. The district nursing service in Wolverhampton monitors the provision of services across the town to ensure high quality care for all patients.

Activities of Daily Living↗