Comparison of Carina active middle-ear implant with conventional hearing aids for mixed hearing loss.

OBJECTIVE: To compare the auditory outcomes of Carina middle-ear implants with those of conventional hearing aids in patients with moderate-to-severe mixed hearing loss. METHODS: The study comprised nine patients (six males, three females) who underwent middle-ear implantation with Carina fully implantable active middle-ear implants to treat bilateral moderate-to-severe mixed hearing loss. The patients initially used conventional hearing aids and subsequently received the Carina implants. The hearing thresholds with implants and hearing aids were compared. RESULTS: There were no significant differences between: the pre-operative and post-operative air and bone conduction thresholds (p > 0.05), the thresholds with hearing aids and Carina implants (p > 0.05), or the pre-operative (mean, 72.8 ± 19 per cent) and post-operative (mean, 69.9 ± 24 per cent) speech discrimination scores (p > 0.05). One of the patients suffered total sensorineural hearing loss three months following implantation despite an initial 38 dB functional gain. All except one patient showed clinical improvements after implantation according to quality of life questionnaire (Glasgow Benefit Inventory) scores. CONCLUSION: Acceptance of Carina implants is better than with conventional hearing aids in patients with mixed hearing loss, although both yield similar hearing amplification. Cosmetic reasons appear to be critical for patient acceptance.

Validity and reliability study of the Turkish version of Spinal Cord Independence Measure-III.

STUDY DESIGN: This is a multicenter, prospective study. OBJECTIVES: The objective of this study was to assess the validity and reliability of the Turkish version of Spinal Cord Independence Measure-III (SCIM-III). SETTING: This study was conducted in rehabilitation centers of three hospitals in Turkey. METHODS: Two-hundred and four (n=204) consecutive patients with spinal cord injury (SCI) were included in the study. Each patient was examined by two physicians. Neurologic impairment was measured according to the American Spinal Injury Association (ASIA) Impairment Scale (AIS) 2000 revised criteria. Backward and forward translation of SCIM-III was performed by native speakers in both languages. To measure the validity of SCIM-III, the scores were compared with patients' AIS grades, total motor scores and the Health Survey Short Form-36 (SF-36) subscale scores. SCIM-III was analyzed for test-retest reliability by the same rater on 49 patients during the follow-up evaluations. RESULTS: Total agreement values between raters changed between 75.9 and 100%. Kappa values were all above 0.6, and they were statistically significant. The Pearson's correlation values between the raters were very high and statistically significant. The Cronbach's α-values for the two consecutive raters were 0.865 and 0.896. Test-retest reliability was assessed by paired samples t-test, and no significant difference was observed. SCIM-III and SF-36 physical (r=0.339, P<0.005) and general health scores (r=0.200, P<0.005) showed correlation. All subscales of the SCIM-III, with the exception of self-care, had significant differences in comparison with the AIS grades. SCIM-III total and total motor scores showed correlation (r=0.585, P<0.001). CONCLUSION: The Turkish version of SCIM-III was found to be valid and reliable.

Transmastoid labyrinthectomy for disabling vertigo after cochlear implantation.

OBJECTIVE: To document the use of transmastoid labyrinthectomy in the treatment of disabling vertigo after unilateral cochlear implantation. METHODS: A 58-year-old man with severe-to-profound bilateral sensorineural hearing loss secondary to chronic otitis media underwent cochlear implantation in his right ear with a Pulsar Med-El device. The surgery was uneventful and the electrode was positioned correctly. He had episodic vertigo three months after implant surgery, and medical treatment and aggressive vestibular rehabilitation did not relieve the vertigo attacks. RESULTS: Right transmastoid labyrinthectomy was performed one year after cochlear implantation. The patient's symptoms were immediately relieved, and cochlear implant function was not adversely affected at follow up after three years. CONCLUSION: Transmastoid labyrinthectomy seems to be an effective, safe method for ablating the vestibular end organ after unilateral cochlear implantation.

Intermittent catheterization in patients with traumatic spinal cord injury: obstacles, worries, level of satisfaction.

OBJECTIVES: The aim of this study is to examine the obstacles in people with traumatic spinal cord injury (SCI) face performing intermittent catheterization (IC), also their worries and level of satisfaction. METHODS: Two hundred sixty-nine patients performing IC for at least 3 months were asked to fill-out a questionnaire about their opinions on IC. RESULTS: In total, 69.5% of patients performed IC themselves, 10.4% had performed by their mothers, 7.8% by another caregiver and 7.4% by their spouse. For the 72 (26%) patients unable to apply IC, reasons were insufficient hand function (56.1%), being unable to sit appropriately (35.4%) and spasticity (8.5%). In all, 70% of male patients had insufficient hand function, 20% could not sit and 10% had spasticity while 56.3% of female patients could not sit, 37.5% had insufficient hand function and 63% had spasticity. Difference between sexes was found to be statistically significant (P<0.05). Worries patients had when starting IC were fear of being dependent on IC (50.2%), accidentally injuring self (43.8%), embarrassment (43.2%), causing an infection (40.2%), bleeding (32.7%), fear of feeling pain (30.2%) and hygiene (24.7%). More women felt embarrassment; other items were similar in both sexes. In all, 46.9% of patients had urinary incontinence in intervals. CONCLUSION: In total, 69.5% of patients performed IC themselves. Men's most common obstacle was insufficient hand function while women's was being unable to sit appropriately. Patients' most common worries were being dependent on IC for life. In all, 46.9% had incontinence in intervals; 47.9% said IC improved their life quality; and 97.4% preferred IC over continuous catheterization.

Neurogenic bladder in patients with traumatic spinal cord injury: treatment and follow-up.

STUDY DESIGN: Multi-center, cross-sectional study. OBJECTIVES: Our aim was to evaluate the treatment methods and follow-up of neurogenic bladder in patients with traumatic spinal cord injury retrospectively using a questionnaire. SETTING: Turkey. METHODS: Three hundred and thirty-seven patients who had spinal cord injury for at least 2 years were enrolled from six centers in the neurogenic bladder study group. They were asked to fill-out a questionnaire about treatments they received and techniques they used for bladder management. RESULTS: The study included 246 male and 91 female patients with a mean age of 42±14 years. Intermittent catheterization (IC) was performed in 77.9% of the patients, 3.8% had indwelling catheters, 13.8% had normal spontaneous micturition, 2.6% performed voiding maneuvers, 1.3% used diapers and 0.6% used condom catheters. No gender difference was found regarding the techniques used in bladder rehabilitation (P>0.05). Overall, 63.2% of patients used anticholinergic drugs; anticholinergic drug use was similar between genders (P>0.05). The most common anticholinergic drug used was oxybutynin (40.3%), followed by trospium (32.6%), tolterodine (19.3%) darifenacin (3.3%), propiverine (3.3%) and solifenacin (1.1%). The specialties of the physicians who first prescribed the anticholinergic drug were physiatrists (76.2%), urologists (22.1%) and neurologists (1.7%). Only four patients had previously received injections of botulinum-toxin-A into the detrusor muscle and three of them stated that their symptoms showed improvement. Most of the patients (77%) had regular follow-up examinations, including urine cultures, urinary system ultrasound and urodynamic tests, when necessary; the reasons for not having regular control visits were living distant from hospital (15.3%) and monetary problems (7.7%). Of the patients, 42.7% did not experience urinary tract infections (UTI), 36.4% had bacteriuria but no UTI episodes with fever, 15.9% had 1-2 clinical UTI episodes per year and 5% had ⩾3 clinical UTIs. The clinical characteristics of patients with and without UTI (at least one symptomatic UTI during 1 year) were similar (P>0.05). The frequency of symptomatic UTI was similar in patients using different bladder management techniques (P>0.05). CONCLUSION: The most frequently used technique for bladder rehabilitation in patients with SCI was IC (77.9%). In all, 63.2% of patients used anticholinergic drugs, oxybutynin being the most commonly used drug. Also, 77% of patients had regular control visits for neurogenic bladder; 42.7% did not experience any UTIs.

Elbow problems in paraplegic spinal cord injured patients: frequency and related risk factors--a preliminary controlled study.

STUDY DESIGN: Cross-sectional controlled study. OBJECTIVES: To evaluate the elbow joint with ultrasound in paraplegic patients, determine the related factors and compare it with healthy controls. SETTING: A training and research rehabilitation hospital in Istanbul. METHODS: A total of 30 paraplegic patients and 20 healthy controls were included in the study. Patients demographic data, pain in the elbow joint, level and duration of injury, ambulation status, type of wheelchair used, daily duration of wheelchair and other ambulation equipment usage, transfers being dependent or independent, daily number of push-ups were recorded. Elbow joints were evaluated with ultrasound for presence of fluid and thickness of the triceps tendon. RESULTS: Mean triceps tendon thickness values of the right side were larger in spinal cord injury (SCI) patients when compared with those of healthy controls'. Joint effusion on the right elbow joint was also found to be more common in SCI patients than in normal subjects. Triceps tendon thickness measurements were not found to be correlated with demographic and clinical factors. Seven paraplegic patients (23%) reported that they have pain in the elbow. CONCLUSION: In this preliminary study, our results showed that right elbow effusion was more frequent and right triceps tendon was thicker in SCI patients when compared with healthy subjects.

The effect of low-frequency TENS in the treatment of neuropathic pain in patients with spinal cord injury.

STUDY DESIGN: Prospective, randomized and controlled study. OBJECTIVES: The aim of the study was to investigate the effect of low-frequency transcutaneous electrical nerve stimulation (LF-TENS) in the treatment of neuropathic pain in patients with spinal cord injury (SCI). METHODS: A total of 33 SCI patients with neuropathic pain were included in the study. History, duration, localization and characteristics of pain were recorded. Visual analog scale (VAS) was used to investigate the effect of LF-TENS four times during the day. Patients were randomly assigned to study and control groups. The study group was treated with 30 min of LF-TENS daily for 10 days while the placebo group with 30 min of sham TENS. RESULTS: The mean age of the patients was 36.55±10.36 years. Out of 33 patients, 7 were tetraplegic and 26 were paraplegic. Twenty-three patients had complete SCI while 10 patients had incomplete injuries. Two groups were similar with respect to age, gender, duration, level and severity of injury. In the LF-TENS treatment group, a statistically significant reduction of the VAS values was observed, however, such an effect was not evident in the control group. CONCLUSION: This study revealed that in treatment of neuropathic pain of SCI patients, LF-TENS may be effective. PERSPECTIVE: This article presents LF-TENS may effectively complement pharmacological treatment in patients with SCI and neuropathic pain.

Effects of different bladder management methods on the quality of life in patients with traumatic spinal cord injury.

STUDY DESIGN: Multi-center, cross-sectional study. OBJECTIVES: To investigate the effects of different bladder management methods on the quality of life (QoL) in patients with spinal cord injury (SCI). SETTING: Turkey. METHODS: Consecutive SCI patients (n=195, 74.4% males), for whom at least 6 months had elapsed since the injury, were included and evaluated in five groups: normal spontaneous micturition (NSM), micturition with assisted maneuvers (MAM), aseptic intermittent catheterization by patient (IC-P), aseptic IC by an attendant/caregiver (IC-A) and indwelling catheterization. The King's Health Questionnaire was used to evaluate the patients' QoL. RESULTS: The bladder management groups were similar regarding age, time elapsed since injury, education level, marital and occupational status. There was no difference among the groups in general health perception, personal relationships and sleep/energy domain scores. While the NSM group had generally the lowest scores, that is, better QoL, the IC-A group had the highest scores, that is, poorer QoL, in most of the domains. When the patients were grouped according to the frequency of urinary incontinence or American Spinal Injury Association Impairment Scale grades, no difference was found in the domain scores of the groups except the symptom severity domain scores. No significant difference was found between paraplegic and tetraplegic patients in the King's Health Questionnaire domains. CONCLUSION: The QoL was notably affected in SCI patients in IC-A group and negative effects on emotional status, physical and social activity limitations were observed, as well.

Investigation of cartilage degradation in patients with spinal cord injury by CTX-II.

STUDY DESIGN: Clinical cross-sectional study. OBJECTIVES: To investigate the cartilage degradation by turnover of C-telopeptide fragments of collagen type-II (CTX-II), a molecule specific for articular cartilage in spinal cord injured patients with respect to clinical functional status. SETTING: Physical Medicine and Rehabilitation Clinics, hospital settings. METHODS: In 68 patients with spinal cord injury (SCI) level and severity of lesion, duration of disease, American Spinal Injury Association Impairment Scale (AIS), motor and sensory score, presence of spasticity, functional ambulation score (FAS) and duration of daily ambulation were evaluated. Cartilage degradation was demonstrated by urinary CTX-II (uCTX-II) measured by enzyme-linked immunosorbent assay. T test, analysis of variance and Pearson correlation analysis were used for statistical calculations. RESULTS: uCTX-II level was significantly higher in patients with AIS grade A, non-functional ambulators or in patients who did not ambulate at all (P<0.05). Although AIS grade, lower extremity motor score, FAS score and duration of daily ambulation were found to be correlated (P<0.05) with uCTX-II, duration of disease, level of neurological lesion, presence of spasticity were not. CONCLUSION: This is the first study providing evidence that cartilage degradation is associated with elevated uCTX-II levels in non-ambulating or non-functional ambulating SCI patients. AIS grade A, FAS zero score and no time for daily ambulation were found to cause significant differences in CTX-II level. It may be important to initiate therapeutic programs as soon as possible after SCI to prevent cartilage atrophy.

The effect of pinealectomy, melatonin and leptin hormones on ovarian follicular development in female Syrian hamsters (Mesocricetus auratus).

We studied the effects of melatonin and leptin hormones on ovarian follicular development in intact and pinealectomized female Syrian hamsters. We first monitored the oestrous cycle of the hamsters by the vaginal smear samples throughout a ten day period to start the injections simultaneously in all groups and performed saline, melatonin and leptin hormone injection groups for both control and pinealectomized hamsters. Then the injections were applied for four days starting the oestrus phase of the cycle and the ovaries were removed for preparation of histological analysis. We measured the diameters and the numbers of the follicles and we classified the follicles according to the number of the granulosa cell layer. Leptin hormone injection increased melatonin hormone injection decreased the number and the diameter of the follicles. The stimulating effect of the leptin hormone was more pronounced in the pinealectomized group. The results of the present study indicate that the removal of the pineal gland and leptin hormone administration are playing a stimulatory while melatonin hormone administration is playing an inhibitory role on the follicular development in female Syrian hamsters.

Vestibular evoked myogenic potentials in patients with fibromyalgia syndrome.

OBJECTIVE: To assess vestibular evoked myogenic potentials in patients with fibromyalgia syndrome. METHODS: Twenty-four patients with fibromyalgia syndrome (two men and 22 women) and 21 female controls were included in the study. All patients underwent vestibular evoked myogenic potential testing. RESULTS: Statistical comparison of fibromyalgia patients with control subjects showed a significant difference with respect to n23 latencies and interpeak latencies (p < 0.05). There was no significant difference in p13 latencies, nor in p13 amplitudes, n23 amplitudes or interpeak amplitudes (p > 0.05). CONCLUSIONS: Although patients with fibromyalgia syndrome generally have subjective neurotological symptoms, clinical and laboratory assessments usually fail to detect any objective abnormality. However, it is possible to detect abnormalities on vestibular evoked myogenic potential testing in such patients, indicating dysfunction in the vestibulospinal pathway, possibly in the saccule. Elongation of the n23 latency and of the interpeak latency of waves p13-n23, during vestibular evoked myogenic potential testing, may be a useful, objective indicator demonstrating neurotological involvement in fibromyalgia syndrome patients. Future research investigating the mechanisms of this latency elongation may help increase understanding of the pathogenesis of fibromyalgia syndrome.

Rhythms of serum melatonin in rats with acute spinal cord injury at the cervical and thoracic regions.

OBJECTIVE: To evaluate the serum melatonin levels in acute period of the spinal cord injury (SCI) caused by trauma in the rats. BACKGROUND: Traumatic SCI induces many types of physiological and pathological damage, including hormonal level variations. METHODS: Forty male Sprague-Dawley rats were divided randomly into four groups. In the control group, neither laminectomy nor SCI were performed; only a large laminectomy was performed without SCI in the sham group. In the cervical and thoracic spinal trauma groups, laminectomies at C5-6 and a T6-7 were performed, respectively, followed by clip compression of the spinal cord. Blood samples were drawn 2, 6, 12 and 24 h after the procedures and assayed immediately. RESULTS: The levels of melatonin in the neurotrauma groups were high in the first 2 h, but at the end of sixth hour, melatonin levels increased in sham-operated group, decreased in neurotrauma groups and did not change in control group. At the 12th hour, melatonin levels continued to decrease in thoracic group significantly. At the 24th hour, the melatonin levels decreased in the cervical, control and sham groups, whereas melatonin levels increased in the thoracic group. CONCLUSIONS: The present study revealed that (1) activation of endogen melatonin secretion of the organism starts immediately after the SCI, but it shows a great lowering trend between 2 and 6 h post-SCI, (2) the tetraplegic rats, which had complete injuries at the lower cervical spinal cord, could not produce enough melatonin secretion; on the contrary, the paraplegic rats, which had complete injury at the upper thoracic spinal cord, showed normal melatonin secretion.

Absence of contralateral suppression of transiently evoked otoacoustic emissions in fibromyalgia syndrome.

OBJECTIVE: To assess contralateral suppression of transiently evoked otoacoustic emissions in patients with fibromyalgia syndrome and normal hearing. METHODS: Twenty-four female patients with fibromyalgia syndrome and 24 healthy female controls with normal hearing were assessed using pure tone audiometry and transiently evoked otoacoustic emissions. RESULTS: All patients with fibromyalgia syndrome and all controls had normal hearing on pure tone audiometry. In the patients with fibromyalgia syndrome, the mean transiently evoked otoacoustic emission amplitude was 15.5 +/- 4.8 dB. The mean transiently evoked otoacoustic emission amplitudes after contralateral suppression was 15.5 +/- 4.9 dB. There was no statistically significant difference between the transiently evoked otoacoustic emission amplitudes measured before and after contralateral suppression (p > 0.05). In the controls, the mean transiently evoked otoacoustic emission amplitude was 12 +/- 5 dB. The mean transiently evoked otoacoustic emission amplitudes after contralateral suppression was 11 +/- 4.7 dB. There was a statistically significant decrease in transiently evoked otoacoustic emission amplitudes after contralateral suppression (p < 0.01). CONCLUSION: The mechanisms related to contralateral suppression of transiently evoked otoacoustic emissions seem dysfunctional in fibromyalgia syndrome. This dysfunction may be at the brain stem level, where the medial superior olivary complex is located, or at the synapses of medial superior olivary complex fibres with the outer hair cells in the cochlea. Demonstration of lack of contralateral suppression of transiently evoked otoacoustic emissions can be used as a diagnostic tool in patients with fibromyalgia syndrome.

Subclinical dysfunction of cochlea and cochlear efferents in migraine: an otoacoustic emission study.

Otoacoustic emission (OAE) testing enables us to identify the cochlear component of a hearing disorder and to monitor objectively minute changes in cochlear status undetectable by other audiological methods. Contralateral sound-induced suppression is mediated by medial superior olivary complex efferents which induce hyperpolarization counteracting the amplifying effects of outer hair cell (OHC) activity. The aim of this study was to assess functions of cochlea and its efferents in migraine using OAE testing and contralateral suppression of transiently evoked OAEs (TEOAE). Fifty-three migraineurs (106 ears) and 41 healthy subjects (82 ears) were included and pure tone audiometry (PTA), speech discrimination scores (SDS), distortion product OAE (DPOAE), TEOAE and contralateral suppression of TEOAEs were tested. PTA and SDS of migraineurs and controls were not different (P > 0.05). DPOAEs were tested between 1 and 6 kHz and a significant difference was detected only at 5 kHz frequency, where DPOAE amplitudes in migraine with aura (MA) were lower than in controls (P < 0.03). The mean amplitudes of TEOAEs were statistically insignificant between controls and migraine groups. Contralateral sound stimulus induced significant decrease in amplitudes of TEOAE (P = 0.005) in controls. In patients with migraine without aura and MA, mean amplitudes of TEOAEs were not suppressed by contralateral sound stimulus (P > 0.05). As PTA, SDS and DPOAE tests demonstrate normal functioning of inner ear between 1 and 4 kHz, absence of suppression of the TEOAEs by contralateral sound stimulation indicates the presence of dysfunction either in the medial olivocochlear complex in the brainstem or at the synaptic transmission between olivocochlear efferents and OHCs in the cochlea. Disruption in the contralateral suppression may be one of the mechanisms predisposing to the phonophobia symptom associated with migraine headache.

Prevention of adhesion to prosthetic mesh in incisional ventral hernias: comparison of different barriers in an experimental model.

BACKGROUND: The purpose of this study was to compare the intra-abdominal adhesion formation following ventral hernia repair by using oxidized regenerated cellulose (ORC) as a barrier underneath polypropylene mesh (PPM), and sodium hyaluronate/carboxymethylcellulose (HA/CMC)-coated PPM. METHODS: A ventral abdominal defect was created in each of 30 male rats which were divided into three groups. In group 1 (control) the defect was repaired with PPM; in group 2 ORC was laid over the viscera and the defect was repaired with PPM, and in group 3 HA/CMC-coated PPM was used for the repairing procedure. On the 28th postoperative day all the rats were sacrificed and adhesions were evaluated by laparoscopic exploration followed by histopathological examination. RESULTS: Animals treated with ORC and PPM, and HA/CMC-coated PPM showed significantly less adhesions than the control group (p = 0.026) and the intra-abdominal adhesions of the rats in these two groups were significantly easier to release than in the control group (p = 0.001). There was no significant difference between the ORC and HA/CMC groups. CONCLUSIONS: ORC used together with PPM is as effective as HA/CMC-coated PPM and ORC can be used as an adhesion barrier in intra-abdominal hernia repair.

Assessment of the ear and otoacoustic emission findings in fibromyalgia syndrome.

OBJECTIVE: We aimed to assess otoacoustic emission (OAE) findings in fibromyalgia (FM) syndrome. METHODS: Thirty-two ears of 16 female patients with FM syndrome and 30 ears of 15 healthy female controls were also included in the study. Pure tone audiometry, speech discrimination testing, tympanometry and otoacoustic emission testing (both transiently evoked and distortion product) were performed. RESULTS: There was no significant difference between the pure tone hearing results of the patients and controls (p > 0.05). There was no significant difference between the distortion-product-otoacoustic emission results of the patients and controls. Audiologic findings of the patients with and without otologic symptoms were not significantly different than controls (p > 0.05). CONCLUSION: Although FM patients generally have subjective symptoms related to ear, clinical or laboratory assessments usually fail to find out any objective finding related to these subjective symptoms. The otologic functions seem spared in FM syndrome.

A test of the coincidence and duration models of melatonin action in Siberian hamsters: the effects of 1-hr melatonin infusions on testicular development in intact and pinealectomized prepubertal Phodopus sungorus.

The pineal hormone melatonin is known to play an important role in mediating photoperiodic messages to the reproductive system in seasonal breeding animals. Our goal was to test, in a single experimental paradigm, two hypotheses that have been forwarded to describe how the circadian rhythm of pineal melatonin transmits photoperiodic information to the reproductive system: 1) induction, i.e., a short-day effect, occurs when secreted melatonin and a circadian rhythm of sensitivity to melatonin coincide in time; 2) induction occurs following exposure to elevated circulating melatonin levels for a prescribed duration. In order to determine the relative validity of these hypotheses, we investigated the testicular maturation response to 1-hr daily infusions of 10, 25, and 50 ng of melatonin in pinealectomized intact and prepubertal Siberian hamsters (Phodopus sungorus). Animals received, beginning on day 15 of life, programmed subcutaneous infusions of melatonin or vehicle at one of five time points (19:00-20:00, 20:00-21:00, 21:00-22:00, 24:00-01:00, and 03:00-04:00 hr) for 15 days. In animals gestated and raised in a long photoperiod (LD16:8 = 16L, where L is the duration of light in hours, and D that of dark), melatonin infusion right after lights off (20:00-21:00 hr) significantly retarded gonadal maturation; this dose was ineffective at other times tested. Doses of 10 and 25 ng melatonin were ineffective at all time points. Identical results were obtained in prepubertal hamsters gestated in a short photoperiod (LD10:14 = 10L) and raised in 16L; these results were independent of the presence or absence of the pineal gland. In animals gestated and raised in 10L, melatonin infusions failed to suppress testicular development beyond that induced by the photoperiod; testicular development was maximally suppressed in all groups. The results of these investigations are best explained under the experimental conditions employed here: 1) the photoperiodic gonadal response in juvenile Siberian hamsters is regulated by the coincidence in time of exogenously administered melatonin with an intrinsic rhythm of sensitivity to melatonin, which, under the constraints imposed by our experimental design, occurred at 20:00-21:00 hr; and 2) the duration of the melatonin signal alone, equal in all groups, cannot explain the results.

A test of the coincidence and duration models of melatonin action in Siberian hamsters. II. The effects of 4- and 8-hr melatonin infusions on testicular development of pinealectomized juvenile Siberian hamsters (Phodopus sungorus).

In a previous paper we demonstrated that properly timed 1-hr infusions of 50 ng melatonin effectively suppressed testicular development in juvenile Siberian hamsters. Only melatonin infused between 20:00 and 21:00 hr was effective in animals exposed to 16L (lights off 20:00 hr). In this paper we further investigate the importance of the coincidence and duration hypotheses of daily exposure of melatonin. Prepubertal Siberian hamsters received either 4- or 8-hr melatonin infusions at various times either on long photoperiod (LD 16:8 = 16L) or on short photoperiod (LD 10:14 = 10L). Daily 8-hr melatonin infusions suppressed testicular development in both photoperiods. Daily 4-hr, 50 ng/hr, melatonin infusions at 17:00-21:00 hr inhibited testicular growth in 16L and daily 4-hr melatonin infusions (either 50 ng/h or 50 ng/day) inhibited testicular growth at 17:00-21:00 hr in 10L. We also tested the efficacy of an interrupted melatonin infusion of long duration (8 hr). Pinealectomized prepubertal male Siberian hamsters, born on 16L, were infused with two signals of 4 hr separated by an interval of 2 hr. Melatonin-infused groups had significantly inhibited testicular growth compared to vehicle-infused animals. Testicular development was maximally inhibited only in those groups in which the period of melatonin sensitivity identified in the previous paper (20:00-21:00 hr) overlapped or immediately followed a period of melatonin infusion. Considering the restrictions of the experimental design employed in these studies, the results are best explained by the hypothesis that the photoperiodic gonadal response in juvenile Siberian hamsters is regulated by the coincidence in time of exogenously administered melatonin with an intrinsic rhythm of sensitivity to melatonin, which occurred at 20:00-21:00 hr. The duration of the melatonin signal alone can not explain the results.

The impact of photoperiods and melatonin on gonadal development in juvenile Turkish hamsters (Mesocricetus brandti).

The reproductive response of both intact adult and juvenile Turkish hamsters has been thoroughly studied and shown to be similar, unlike the golden hamster where juveniles remain aphotoperiodic until approximately 8 weeks of age. Unstudied to date, however, is the role of the pineal and its hormone melatonin in generating the testicular response to photoperiod in juvenile Turkish hamsters. Therefore, in this study we examined the reproductive response of prepubertal male Turkish hamsters, subjected to four different photoperiods (8L:16D, 16L:8D, 20L:4D, and 24L:0D) with altered pineal gland function. At 15 days of age, long-day-born (16L:8D) hamsters were either pinealectomized, received melatonin implants, or remained untreated. Testes sizes were measured every 2 weeks. Testicular growth occurred only in untreated and beeswax implanted groups in 16L:8D. Exposure to other photoperiods inhibited testicular development in untreated and beeswax implanted animals. Removal of the pineal gland, masking of the daily melatonin rhythm with constant release subcutaneous melatonin implants, or eliminating the daily rhythm of melatonin by continuous light exposure resulted in inhibition of gonadal development. These results demonstrate that juvenile Turkish hamsters respond similarly to adults on all photoperiods and under all conditions of pineal function tested.

Effects of photoperiod, pinealectomy, and melatonin implants on testicular development in juvenile Siberian hamsters (Phodopus sungorus).

When transferred from a long to short photoperiod, Siberian hamsters (Phodopus sungorus) undergo a number of physiological and morphological changes including suppression of gonadal activity, a change in pelage color, a decrease in body weight, and, in response to a simultaneous decrease in ambient temperature, physiological changes associated with the induction of daily torpor. All these functions can be affected by photoperiod and melatonin treatment. To investigate the interactive effects of photoperiod, pinealectomy, and melatonin on gonadal development, two experiments were performed using juvenile Siberian hamsters. In experiment 1, animals born in a long photoperiod (16L:8D) either remained in a long photoperiod or were transferred to a short photoperiod (8L:16D) from 15 days of age, when surgeries (pinealectomy and/or melatonin implantation) were performed. Testicular development was inhibited in all animals bearing melatonin implants irrespective of the presence or absence of the pineal gland. Pinealectomy blocked the inhibitory effect of short photoperiod on maturation of the reproductive system. Therefore, the pineal gland must be involved in the short photoperiod- induced inhibition of testicular maturation of juvenile Siberian hamsters. In experiment 2, a similar experimental design was employed except that the hamsters were born and raised to 15 days of age in 8L:16D. Exogenous melatonin, pinealectomy, or both retarded gonadal development in hamsters born in 8L:16D and transferred on Day 15 of age to 16L:8D. All hamsters maintained in a short photoperiod had small testes irrespective of the presence of absence of the pineal gland or of melatonin implants. Hamsters transferred to a long photoperiod after pinealectomy and/or melatonin implantation had small testes compared to those of the control group.(ABSTRACT TRUNCATED AT 250 WORDS)