Fat Sand Rats Research Articles

GPER1 in sand rat epididymis: Effects of seasonal variations, castration and efferent ducts ligation

Estrogen plays a crucial role in regulating epididymal function and development. Estrogen signaling is mediated via two main receptors essentially involved in the genomic regulating pathway: ERα and ERβ. Recent studies revealed the contribution of a novel estrogen receptor involved in the non-genomic pathway: GPER1. This receptor belongs to the family of seven-transmembrane G-protein-coupled receptors and it triggers rapid cellular responses. Immuno-histochemical studies and Western Blot analyses were performed to investigate the GPER1 expression in the caput and cauda epididymis of free-ranging fat sand rats (Psammomys obesus) captured during the breeding and resting seasons. We also investigated the effect of castration (C), castration followed by testosterone treatment (C+T), and ligation of the efferent ducts (L). During the breeding season, a marked positive GPER1 immunoreactivity was detected in the cytoplasm of principal cells and basal cells; this signal persisted during the resting season, attenuated however, meanwhile the clear cells were not immuno-reactive. In C animals, the immuno-histochemical staining underwent nuclear translocation. In C+T animals, this response became nuclear and cytoplasmic. In the L group, the expression of the GPER1 was mainly located in the cytoplasm of principal cells and in the nuclei of basal cells; the sperm was also immune-positive in the cauda epididymis. Western blot analysis showed that GPER1 has a molecular weight of 55kDa in the caput and cauda epididymis during the breeding season, and it persisted during the resting season in the caput epididymis with a decrease in the cauda epididymis. These results suggest that GPER1 mediate a specific cellular estrogen signaling with marked differences between the breeding and resting seasons. Experimental groups suggest that testosterone is involved in the regulation of the expression of GPER1, in addition to other estrogen signalization pathways.

Seasonal variations of aromatase and estrogen receptors expression in the testis of free-ranging sand rats

An increasing number of studies revealed the importance of estrogen in male reproduction. However, most research was conducted in laboratory rodents subjected to standardized environmental conditions. Therefore, seasonal regulations of estrogen pathways remain poorly understood under natural conditions. Using immunohistochemistry, the expression of several molecules involved in the functioning of testis (i.e. 17-β estradiol [E2], P450 aromatase, estrogen receptors ESR1, ESR2, and GPER1 [also known as GPR30]) were investigated in free-ranging fat sand rats, Psammomys obesus, during the breeding and resting seasons. Leydig cells showed a strong immunoreactivity for aromatase in the testis sampled during the breeding season only; however, E2, ESR1, ESR2 and GPER1 were present during both seasons. Sertoli cells showed a positive signal for E2 and ESR2 during the breeding season; though, all molecules, except GPER1, were present during the resting season. Spermatogonia were reactive for E2, ESR2 and GPER1 during the breeding season and for ESR1 and GPER1 during the resting season. During both seasons, spermatocytes-I presented a moderate reactivity for E2, ESR1, ESR2 and a strong reactivity for GPER1; aromatase was detected during the resting season only. Spermatids and spermatozoa were present exclusively during breeding season and were reactive for all molecules; except round spermatids that were negative for aromatase. The functioning of the testis depends on finely tuned stimulation and inhibition systems. Our results suggest that differential expression of aromatase, ESR1, ESR2, and GPER1 across cells types is involved in the seasonal activation/inactivation cycle of spermatogenesis in a free-ranging species.

The transition from day-to-night activity is a risk factor for the development of CNS oxygen toxicity in the diurnal fat sand rat (Psammomys obesus)

ABSTRACTPerformance and safety are impaired in employees engaged in shift work. Combat divers who use closed-circuit oxygen diving apparatus undergo part of their training during the night hours. The greatest risk involved in diving with such apparatus is the development of central nervous system oxygen toxicity (CNS-OT). We investigated whether the switch from day-to-night activity may be a risk factor for the development of CNS-OT using a diurnal animal model, the fat sand rat (Psammomys obesus). Animals were kept on a 12:12 light–dark schedule (6 a.m. to 6 p.m. at 500 lx). The study included two groups: (1) Control group: animals were kept awake and active during the day, between 09:00 and 15:00. (2) Experimental group: animals were kept awake and active during the night, between 21:00 and 03:00, when they were exposed to dim light in order to simulate the conditions prevalent during combat diver training. This continued for a period of 3 weeks, 5 days a week. On completion of this phase, 6-sulphatoxymelatonin (6-SMT) levels in urine were determined over a period of 24 h. Animals were then exposed to hyperbaric oxygen (HBO). To investigate the effect of acute melatonin administration, melatonin (50 mg/kg) or its vehicle was administered to the animals in both groups 20 min prior to HBO exposure. After the exposure, the activity of superoxide dismutase, catalase and glutathione peroxidase was measured, as were the levels of neuronal nitric oxide synthase (nNOS) and overall nitrotyrosylation in the cortex and hippocampus. Latency to CNS-OT was significantly reduced after the transition from day-to-night activity. This was associated with alterations in the level of melatonin metabolites secreted in the urine. Acute melatonin administration had no effect on latency to CNS-OT in either of the groups. Nevertheless, the activity of superoxide dismutase and catalase, as well as nitrotyrosine and nNOS levels, were altered in the hippocampus following melatonin administration. On the basis of these results, we suggest that a switch from diurnal to nocturnal activity may represent an additional risk factor for the development of CNS-OT. Utilizing a diurnal animal model may contribute to our understanding of the heightened risk of developing CNS-OT when diving with closed-circuit oxygen apparatus at night.

Hearing loss patterns after cochlear implantation via the round window in an animal model

PurposeThe mechanism and the type of hearing loss induced by cochlear implants are mostly unknown. Therefore, this study evaluated the impact and type of hearing loss induced by each stage of cochlear implantation surgery in an animal model. Study designOriginal basic research animal study. SettingThe study was conducted in a tertiary, university-affiliated medical center in accordance with the guidelines of the Institutional Animal Care and Use Committee. Subjects and methodsCochlear implant electrode array was inserted via the round window membrane in 17 ears of 9 adult-size fat sand rats. In 7 ears of 5 additional animals round window incision only was performed, followed by patching with a small piece of periosteum (control). Hearing thresholds to air (AC) and bone conduction (BC), clicks, 1kHz and 6kHz tone bursts were measured by auditory brainstem evoked potential, before, during each stage of surgery and one week post-operatively. In addition, inner ear histology was performed. ResultsThe degree of hearing loss increased significantly from baseline throughout the stages of cochlear implantation surgery and up to one week after (p<0.0001). In both operated groups, the greatest deterioration was noted after round window incision. Overall, threshold shift to air-conduction clicks, reached 61dB SPL and the bone conduction threshold deteriorated by 19dB SPL only. Similar losses were found for 1-kHz and 6-kHz frequencies. The hearing loss was not associated with significant changes in inner ear histology. ConclusionsHearing loss following cochlear implantation in normal hearing animals is progressive and of mixed type, but mainly conductive. Changes in the inner-ear mechanism are most likely responsible for the conductive hearing loss.

Hearing Loss After Vestibular Implantation in Sand Rats With Normal Hearing.

Bilateral vestibular failure is a debilitating condition that may lead to oscillopia and adversely affect quality of life. Researchers have suggested that vestibular function might be restored with implantation of an external mechanical stimulation device. However, it is essential that such a device must not interfere with normal hearing. To evaluate the effect of vestibular implant insertion on hearing in a sand rat model with normal hearing. The study was conducted in a tertiary medical center in accord with the guidelines of the Rabin Medical Center Animal Care and Use Committee. The experiment was performed in 6 adult, 6-month-old, fat sand rats (Psammomys obesus), which have a unique aural anatomy that permits access to the inner ear. The study dates were March 2013 to March 2014. The sand rats were anesthetized and electrodes were implanted unilaterally (in 6 sand rats) or bilaterally (in 2 sand rats) in all 3 semicircular canals (lateral, then posterior, and then superior) by fenestration of the respective ampullas. To measure air and bone conduction thresholds, auditory nerve brainstem evoked responses to alternating polarity clicks and 1-kHz tone bursts were tested before surgery, at each operative stage, and after surgery. Air or bone conduction threshold shifts after implantation of a vestibular implant electrode array in each semicircular canal. After unilateral implantation of the vestibular implant, sand rats showed a sideways head tilt, whereas after bilateral implantation, sand rats ran around in circles and were unable to stand still or walk on a treadmill. On statistical analysis, statistically significant differences from preoperative values were obtained across all stages of surgery for air conduction thresholds. The largest and statistically significant air conduction shift for 1-kHz stimuli (mean [SD, 13.7 [2.8] dB; P < .004) as well as for clicks (12.5 [2.1] dB; P < .002) was found for the superior canal electrode insertion. For the posterior canal, the air conduction thresholds to 1-kHz stimuli and to clicks shifted significantly after electrode insertion (mean [SD], 7.5 [2.3] dB; P < .01 and 7.5 [0.9] dB; P < .001). For the lateral canal, only the threshold to clicks changed significantly (mean [SD], 5.5 [1.7] dB; P < .02). Bone conduction thresholds did not change significantly after vestibular electrode insertion. Implantation of a vestibular device is associated with mild to moderate conductive hearing loss in fat sand rats with normal hearing, especially when the device is placed in the posterior and superior semicircular canals. Bilateral implantation is associated with major vestibular pathologic results. Further studies are needed in animals with cochlear or vestibular disorders before it can be definitively concluded that vestibular implantation carries only a minor risk to hearing.

Voluntary exercise enhances activity rhythms and ameliorates anxiety- and depression-like behaviors in the sand rat model of circadian rhythm-related mood changes

Physical exercise is a non-pharmacological treatment for affective disorders. The mechanisms of its effects are unknown although some suggest a relationship to synchronization of circadian rhythms. One way to explore mechanisms is to utilize animal models. We previously demonstrated that the diurnal fat sand rat is an advantageous model for studying the interactions between photoperiods and mood. The current study was designed to evaluate the effects of voluntary exercise on activity rhythms and anxiety and depression-like behaviors in sand rats as a step towards better understanding of the underlying mechanisms.Male sand rats were housed in short photoperiod (SP; 5h light/19h dark) or neutral light (NP; 12h light/12h dark) regimens for 3weeks and divided into subgroups with or without running wheels. Activity was monitored for 3 additional weeks and then animals were tested in the elevated plus-maze, the forced swim test and the social interaction test.Activity rhythms were enhanced by the running wheels. As hypothesized, voluntary exercise had significant effects on SP animals' anxiety- and depression-like behaviors but not on NP animals.Results are discussed in the context of interactions between physical exercise, circadian rhythms and mood. We suggest that the sand rat model can be used to explore the underlying mechanism of the effects of physical exercise for mood disorders.

Changes in the immunolocalization of estrogen and progesterone receptors in the endometrium of the sand rat during the estrous cycle

Objective The aim of this work was to characterize the reproductive function of a diurnal rodent, the fat sand rat, considered such as a model for studying several metabolism diseases. Uterine preliminary immunohistological results are presented. Materiel et methods After antigen retrieval, immunohistochemistry method was applied on paraffin embedded uterine. Results At estrus and diestrus, labeling of ERs was in the cytoplasm of all epithelial cells ; in metestrus, labeling became both nuclear and in the cytoplasm with few unlabeled cells, the stroma was slightly labeled ; at proestrus label for ERs and PRs was localized in the nuclear fraction. During estrus, PRs, were localized in the nuclear fraction of epithelial and stroma cells; in the lining epithelium, predominate cells were labeled while glandular cells remained immunonegative; in the stroma, labeled cells predominated. In metestrus, labeled PRs were nuclear and cytoplasmic in epithelial cells and only nuclear in the stroma. At diestrus, lining and glandular epithelial cells were completely immunonegative; labeled PRs persisted in the stroma. At proestrus, two cases were observed : negative staining of epithelial tissue and positive in the nuclear fraction of stroma cells in some female and nuclear positive staining of the epithelial and stroma cells in other females. Conclusion The localization of ERs and PRs varied during the cycle, therefore estradiol and progesterone act at different uterine compartment during the estrous phases. Functional modifications correlated with receptors localization will be presented.

The mechanism of direct stimulation of the cochlea by vibrating the round window.

Active middle ear implants such as the vibrant sound bridge (VSB) have been placed on the round window (RW) in patients with conductive or mixed hearing loss, with satisfactory hearing results. Several observations show that the mechanism of RW stimulation is not completely understood. The purpose of the present study was to compare different coupling procedures between the transducer and the RW in order to contribute to an understanding of the mechanism of RW stimulation. Five fat sand rats underwent ablation of the left ear and opening of the right bulla, followed by baseline measurements of thresholds of auditory nerve brainstem evoked responses (ABR) to air and bone conduction click stimuli. Subsequently the malleus and incus were removed from the right middle ear, modeling a conductive hearing loss in which the VSB on the RW is indicated. In the next stage of the experiment, a rod attached to the bone vibrator was placed gently on the RW membrane and then on saline fluid applied to the RW niche. ABR thresholds were recorded following both placements. Mean baseline ABR threshold in response to air conduction stimuli was 48 ± 4 dB; mean ABR threshold when the rod was placed on the dry RW membrane was 99 ± 12 dB; mean ABR threshold when the rod was in the saline on RW niche was 79 ± 7 dB. ABR thresholds were better (lower) with stimulation of fluid on the RW membrane compared to direct stimulation of the RW, providing further evidence of a direct fluid pathway.

Air, bone and soft tissue excitation of the cochlea in the presence of severe impediments to ossicle and window mobility

Clinical conditions have been described in which one of the two cochlear windows is immobile (otosclerosis) or absent (round window atresia), but nevertheless bone conduction (BC) thresholds are relatively unaffected. To clarify this apparent paradox, experimental manipulations which would severely impede several of the classical osseous mechanisms of BC were induced in fat sand rats, including discontinuity or immobilization of the ossicular chain, coupled with window fixation. Effects of these manipulations were assessed by recording auditory nerve brainstem evoked response (ABR) thresholds to stimulation by air conduction (AC), by osseous BC and by non-osseous BC (also called soft tissue conduction-STC) in which the BC bone vibrator is applied to skin sites. Following the immobilization, discontinuity and window fixation, auditory stimulation was also delivered to cerebro-spinal fluid (CSF) and to saline applied to the middle ear cavity. While the manipulations (immobilization, discontinuity, window fixation) led to an elevation of AC thresholds, nevertheless, there was no change in osseous and non-osseous BC thresholds. On the other hand, ABR could be elicited in response to fluid pressure stimulation to CSF and middle ear saline, even in the presence of the severe restriction of ossicular chain and window mobility. The results of these experiments in which osseous and non-osseous BC thresholds remained unchanged in the presence of severe restriction of the classical middle ear mechanisms and in the absence of an efficient release window, while ABR could be recorded in response to fluid pressure auditory stimulation to fluid sites, indicate that it is possible that the inner ear may be activated at low sound intensities by fast fluid pressure stimulation. At higher sound intensities, a slower passive basilar membrane traveling wave may serve to excite the inner ear.

Diurnal rodents as an advantageous model for affective disorders: novel data from diurnal degu (Octodon degus)

Circadian rhythms are strongly associated with affective disorders and recent studies have suggested utilization of diurnal rodents as model animal for circadian rhythms-related domains of these disorders. Previous work with the diurnal fat sand rat and Nile grass rat demonstrated that short photoperiod conditions result in behavioral changes including anxiety- and depression-like behavior. The present study examined the effect of manipulating day length on activity rhythms and behavior of the diurnal degu. Animals were housed for 3weeks under either a short photoperiod (5-h:19-h LD) or a neutral photoperiod (12-h:12-h LD) and then evaluated by sweet solution test and the forced swim test for depression-like behavior, and in the light/dark box and open field for anxiety-like behavior. Results indicate that short photoperiod induced depression-like behavior in the forced swim test and the sweet solution preference test and anxiety-like behavior in the open field compared with animals maintained in a neutral photoperiod. No effects were shown in the light/dark box. Short photoperiod-acclimated degu showed reduced total activity duration and activity was not restricted to the light phase. The present study further supports the utilization of diurnal rodents to model circadian rhythms-related affective change. Beyond the possible diversity in the mechanisms underlying diurnality in different animals, there are now evidences that in three different diurnal species, the fat sand rat, the grass Nile rat and the degu, shortening of photoperiod results in the appearance of anxiety- and depression-like behaviors.

Immunolocalization of estrogen and androgen receptors in the caput epididymidis of the fat sand rat (Psammomys obesus): Effects of seasonal variations, castration and efferent duct ligation

The fat sand rat (Psammomys obesus) is a model to study seasonal reproductive cycle changes and several metabolic disorders. In order to show a possible involvement of estrogens in the male reproductive functions, the expression of estrogen receptors (ESR1 and ESR2) and androgen receptor (AR) were investigated in the caput epididymidis of fat sand rats during the breeding season, resting season, after castration, after castration followed by testosterone treatment, and after ligation of efferent ducts. In the breeding season, principal cells presented a strong immunostaining of AR in both nuclei and cytoplasm, a strong staining of ESR1, mainly in the apical zone, and a strong immunoexpression of ESR2, mainly in nuclei. In the resting season, a moderate immunostaining of AR in both cytoplasm and nuclei was observed. ESR1 staining showed a strong immunoreactivity in the nuclei. In contrast, the nuclei were negative for ESR2. After castration, a low and selective signal distribution was observed: the nuclei were moderately positive for AR and ESR2, and negative for ESR1. After castration and testosterone treatment, an androgen-dependence for AR and the restoration of ESR1 but not ESR2 immunoexpression were observed. After ligation of the efferent ducts, a considerable reduction of AR immunoreactivity was observed in contrast to ESR1 and ESR2, which gave a strong immunostaining signal. These results illustrate the complexity of the regulation of the androgen and estrogen receptor expression in the epididymis and argue for the coexistence of both androgenic and estrogenic pathways.

Mutual masking in the cochlea by bone conduction stimulation and by soft tissue conduction stimulation in an animal model

Soft tissue conduction (STC) is a recently described mode of auditory stimulation in which vibrations induced by a clinical bone vibrator applied to soft tissue sites on the head, neck, and thorax of human subjects reach the cochlea and elicit auditory sensation. In humans, STC stimulation interacts with air conduction stimulation and with bone conduction (BC) stimulation in several ways, e.g., mutual masking. This study investigated whether mutual masking between STC and BC stimulation can be demonstrated in an experimental animal. In fat sand rats, auditory nerve and brainstem evoked response to BC stimulation was recorded in the presence of noise masking presented by STC and vice versa. STC successfully masked BC, and BC also masked STC responses. Mutual masking, now demonstrated in animals, paves the way for animal experiments to clarify the pathway between the STC stimulation sites and the cochlea.

Activity Rhythms and Masking Response in the Diurnal Fat Sand Rat Under Laboratory Conditions

Daily rhythms are heavily influenced by light in two major ways. One is through photic entrainment of a circadian clock, and the other is through a more direct process, referred to as masking. Whereas entraining effects of photic stimuli are quite similar in nocturnal and diurnal species, masking is very different. Laboratory conditions differ greatly from what is experienced by individuals in their natural habitat, and several studies have shown that activity patterns can greatly differ between laboratory environment and natural condition. This is especially prevalent in diurnal rodents. We studied the daily rhythms and masking response in the fat sand rat (Psammomys obesus), a diurnal desert rodent, and activity rhythms of Tristram’s jird (Meriones tristrami), a nocturnal member of the same subfamily (Gerbillinae). We found that most sand rats kept on a 12 h:12 h light-dark (LD) cycles at two light intensities (500 and 1000 lux) have a nocturnal phase preferences of general activity and higher body temperature during the dark phase. In most individuals, activity was not as stable that of the nocturnal Tritram’s jirds, which showed a clear and stable nocturnal activity pattern under the same conditions. Sand rats responded to a 6-h phase advance and 6-h phase delay as expected, and, under constant conditions, all tested animals free ran. In contrast with the nocturnal phase preference, fat sand rats did not show a masking response to light pulses during the dark phase or to a dark pulse during the light phase. They did, however, have a significant preference to the light phase under a 3.5 h:3.5 h LD schedule. Currently, we could not identify the underlying mechanisms responsible for the temporal niche switch in this species. However, our results provide us with a valuable tool for further studies of the circadian system of diurnal species, and will hopefully lead us to understanding diurnality, its mechanisms, causes, and consequences.

Effect on Auditory Threshold of Air and Water Pockets Bordering the Pathway between Soft Tissue Stimulation Sites and the Cochlea

Auditory sensation can be elicited by applying a bone conduction vibrator to skin sites on the head, neck, and thorax over soft tissues. This is called soft tissue conduction (STC). We hypothesized that introducing substances with acoustic impedances that sharply deviate from those of soft tissues, such as air pockets, into the soft tissues beneath soft tissue stimulation sites would have an effect on the auditory threshold to stimulation at skin sites over soft tissue. In human subjects, we assessed the auditory threshold with a bone vibrator applied to several STC sites, especially the cheek, and to several bone conduction sites on the skull. The subjects were equipped with bilateral earplugs. The subject then filled his or her cheek with either air or water, and the auditory threshold was again determined. We also recorded the auditory brain stem response to STC stimulation under the chin in fat sand rats in the absence and presence of subcutaneous air or saline solution pockets (0.4 mL) under the chin. In humans, the threshold to stimulation on the cheek was elevated (13 to 18 dB) in the presence of an air-inflated cheek, but not with a water-filled cheek. In animals, in the presence of an air pocket, the auditory brain stem response threshold was elevated by 10 to 20 dB; no threshold change occurred with a saline solution pocket. The introduction of air (but not water) into the soft tissues beneath the soft tissue stimulation sites led to a threshold elevation in both humans and animals. This was not the case when an identical volume of water was introduced, which would also have interrupted a possible parallel bone conduction pathway. These results provide evidence that soft tissue stimulation at low intensities induces tissue vibrations that are transmitted to the cochlea along a series of soft tissues with similar acoustic impedances.

Assessment of inner ear bone vibrations during auditory stimulation by bone conduction and by soft tissue conduction

Soft tissue conduction (STC), a recently described mode of auditory stimulation elicited when the clinical bone vibrator is applied to skin sites over the head, neck, and thorax, complements air conduction (AC) and bone conduction (BC), elicited by the same vibrator. The study assessed skull bone vibrations induced during STC and BC stimulation. The experiments were conducted on fat sand rats. Thresholds of auditory nerve brainstem evoked responses (ABRs) were recorded and compared to the lowest-intensity sound stimuli that elicited vibrations at the bony vestibule of the inner ear detected by a laser Doppler vibrometer. Vibrations were detected during BC but not during STC stimulation. ABR was recorded to both STC and to BC stimulation. Low-intensity STC stimulation does not induce vibrations of the inner ear, showing that STC apparently does not involve mechanisms based on vibrations of bone.

Effect of Cochlear Window Fixation on Air- and Bone-Conduction Thresholds

In the absence of patent cochlear windows, cochlear fluid inertia depends on the presence of a "third window" as a major component of the bone-conduction response. Studies have shown conflicting results regarding changes in air and bone conduction whenever, the round window, oval window, or both windows were occluded. The study was performed in a tertiary university-affiliated medical center. Auditory brain responses to clicks and 1-kHz tone bursts delivered by air and bone conduction were tested in 5 adult-size fat sand rats. The round window membrane (total, 7 ears) was sealed with Super Glue, and auditory brain response testing was repeated. Thereafter, the stapes footplate was firmly fixated, and auditory brain responses were recorded for a third time. Round-window fixation induced a significant increase in air-conduction thresholds to clicks from 36.4 ± 0.9 to 69.3 ± 4.1 dB SPL, with no significant change in bone-conduction thresholds. When the stapes footplate was immobilized as well, air conduction increased by another 20 dB, on average, with no change in bone conduction. A similar deterioration was seen in response to 1 kHz stimulus. These findings support and complement earlier studies in the same animal model, suggesting that when the pressure outlet through the cochlear windows are abolished, still bone conduction displaces the cochlear partition probably because of a functioning "third window."

The effect of topically applied antimycotic agents on inner ear vestibular and cochlear function

To assess and compare the effect of commonly used topical antimycotic agents and their solvents on the function of the vestibular and cochlear parts of the sand rat's inner ear. Prospective, controlled, animal study. Forty-five fat sand rats were randomly assigned to five major groups, each receiving topical application of a different agent: saline (control), gentamicin (ototoxic control), and three antimycotic agents: nystatin, clotrimazole solution (Agisten), and bifonazole solution (Agispor). All animals underwent a right labyrinthectomy, and a polyethylene tube was inserted into the left middle ear followed by baseline recording of vestibular evoked potentials (VsEPs) and auditory nerve and brainstem responses (ABR). Subsequently, each animal received five consecutive daily applications of the specific agent into the left middle ear. Evoked potential recordings were repeated 3 and 10 days after the last application and compared to baseline. For clotrimazole and bifonazole solutions, the effect of the solvents was assessed by comparing ABR recordings at similar intervals. Administration of saline did not affect VsEPs or ABR. Both could not be recorded following gentamicin application. In all three antimycotic agents, no statistically significant difference was found between VsEPs recordings before and after application. Clotrimazole and bifonazole solutions caused a significant ABR threshold elevation similar to that caused by their solvents. Nystatin caused a less significant ABR threshold elevation. The three commonly used topical antimycotic agents investigated here did not affect vestibular function but had a toxic effect on inner ear cochlear function. It seems the main offenders were the solvents.

Experimental Exploration of the Soft Tissue Conduction Pathway from Skin Stimulation Site to Inner Ear

Auditory sensation can be elicited by air conduction (AC) and by bone conduction (BC). It is also possible to elicit such responses by applying the standard clinical bone vibrator to the skin over soft tissue sites on the head, neck, or thorax of humans and animals. This mode of auditory stimulation has been called soft tissue conduction (STC). This study was designed to investigate the pathway between soft tissue sites and the ear. The air in the middle ear was replaced with saline solution in an animal with unique anatomy--the fat sand rat, in which about 70% of a thin-walled inner ear bulges into the middle ear bulla cavity--while we recorded the auditory brain stem responses (ABRs) to AC, BC, and STC stimulation. This replacement of air with saline solution led to a significant improvement in STC threshold. With AC stimulation, the ABR threshold was elevated and the latency of the first ABR wave was prolonged. Consistent changes were not seen with BC stimulation. When the air (which has a very low acoustic impedance) that normally surrounds most of the inner ear is replaced with saline solution (which has an acoustic impedance similar to that of soft tissues), the STC threshold is improved. This improvement may be due to improved transmission of acoustic energy from the soft tissues to the inner ear.

Effects of morning compared with evening bright light administration to ameliorate short-photoperiod induced depression- and anxiety-like behaviors in a diurnal rodent model

The lack of appropriate animal models for affective disorders is a major factor hindering better understanding of the underlying pathologies and the development of more efficacious treatments. Because circadian rhythms play an important role in affective disorders, we recently suggested that diurnal rodents can be advantageous as model animals. We found that in diurnal rodents, short photoperiod induces depression- and anxiety-like behaviors, with similarities to human seasonal affective disorder. In a pilot study we also found that these behaviors are ameliorated by morning bright light administration. In the present study we further evaluated the effects of morning and evening bright light administration on short photoperiod-induced depression- and anxiety-like behaviors in diurnal fat sand rats. Animals were maintained under short (5L:19D) or neutral (12L:12D) photoperiod and treated with morning or evening bright light or red dim light as control. Morning bright light ameliorated the behavioral deficits in the elevated plus maze and social interaction tests whereas evening bright light was effective only in the social interaction test. This is the first detailed presentation of the effects of bright light treatment in an animal model and a clear demonstration to the advantages of utilizing diurnal rodents to study interactions between circadian rhythms and affect.

Simplified and improved monitoring traps for sampling sand flies

Simplified and improved monitoring traps for sampling sand flies Gunter C. Muller1, Edita, E. Revay2, and John C. Beier3 1Department of Microbiology and Molecular Genetics , IMRIC, Kuvin Centre for the Study of Infectious and Tropical Diseases, Faculty of Medicine, Hebrew University, Jerusalem 91120, Israel, guntercmuller@hotmail.com 2Department of Anatomy and Cell Biology, Bruce Rappaport Faculty of Medicine, Technion, Haifa, Israel 3Department of Epidemiology and Public Health, University of Miami Miller School of Medicine, Miami, FL 33136, U.S.A.