The total number of neurons and calcium binding protein positive neurons during aging in the cochlear nucleus of CBA/CaJ mice: a quantitative study.

The quantitative stereological method, the optical fractionator, was used for determining the total number of neurons and the total number of neurons immunostained with parvalbumin, calbindin-D28k (calbindin), and calretinin in the dorsal and posteroventral cochlear nucleus (DCN and PVCN) in CBA/CaJ (CBA) mice during aging (1-39 months old). CBA mice have only a modest sensorineural pathology late in life. An age-related decrease of the total number of neurons was demonstrated in the DCN (r=-0.54, P<0.03), while the total number of neurons in the PVCN did not show any significant age-related differences (r=0.16, P=0.57). In the DCN 5.5% of neurons were parvalbumin positive in the very old (30-39 months) mice, vs. 2.2% in the 1 month old mice. In the DCN 3% of the neurons were calbindin immunopositive in the 30-39 months mice compared to 1.9% in the 1 month old group. In the PVCN, 20% of the neurons in the very old mice were parvalbumin immunopositive, compared to 12% in the young mice. Calbindin did not show any significant age-related differences in the PVCN. The total number of calretinin immunopositive neurons both in the DCN and PVCN did not show any significant change with increasing age. In conclusion, the total neuronal number in the DCN and PVCN was age-related and region-specific. While the neuronal number in the DCN and PVCN was decreased or unchanged, respectively, the calcium binding protein positive neuronal number showed a graded increase during aging in a region-specific and protein-specific manner.

Peripheral cell loss related to calcium binding protein immunocytochemistry in the dorsal cochlear nucleus in CBA/CaJ mice during aging.

The influence of cochlear hair cell and spiral ganglia neuron loss on calcium binding protein immunoreactivity (calretinin, parvalbumin and calbindin) in the dorsal and posteroventral cochlear nuclei (DCN and PVCN) in CBA/CaJ (CBA) mice during aging (1-39 months) was determined. Since calcium binding proteins have buffering properties against calcium overload, they may have a protective role during aging. It is shown that the percentage of calretinin- and parvalbumin-immunopositive neurons in the DCN showed a statistically significant positive correlation with inner hair cell loss, outer hair cell loss, and spiral ganglion cell loss. A correlation was also found between aging and the auditory periphery, and calcium binding proteins in the DCN. These findings imply that the pathophysiological state of the auditory periphery may influence the neuronal homeostasis in the dorsal cochlear nucleus.

Sound stimulation increases calcium-binding protein immunoreactivity in the inferior colliculus in mice.

The numerical density of calbindin D-28k and parvalbumin immunopositive neurons in the inferior colliculus (IC) in mice was increased after sound stimulation. An increased number of calbindin positive neurons was found in the deep layers of the external cortex (EC) and particularly in the dorsal cortex (DC) and commissural nucleus (NCO). An increase of parvalbumin positive neurons was found in the EC, central nucleus (ICC) and DC, but not in the NCO. The increased immunoreactivity related to sound exposure suggests the appearance of neurons which express these proteins after sound stimulation. The up-regulation of calcium-binding proteins in these neurons may be due to their protective role against overstimulation, their response to a higher auditory metabolic activity, or increasing effect of excitatory inputs after noise-induced hearing loss.

Modulating calbindin and parvalbumin immunoreactivity in the cochlear nucleus by moderate noise exposure in mice. . A quantitative study on the dorsal and posteroventral cochlear nucleus.

The number of calbindin D-28k and parvalbumin immunoreactive (IR) neurons were characterized on sections from the cochlear nucleus, dorsal cochlear nucleus (DCN) and posteroventral cochlear nucleus (PVCN) using two-dimensional quantification. After noise exposure (6-12 kHz, 2 h, at either 80 dB SPL or 103 dB SPL), the number of calbindin and parvalbumin immunoreactive neurons increased in CBA/CBA mice. Quantitative analysis of calbindin-IR in the PVCN did not show a statistically significant difference between any of the groups, whereas statistically significant differences in calbindin-IR were found in the DCN for the 103 dB and 80 dB group compared to the control group, and 103 dB compared to the 80 dB group, respectively. A statistically significant increase in the number of parvalbumin-IR neurons in the PVCN and the DCN was evident in the 103 dB and 80 dB group compared to the control group, and in the 103 dB compared to the 80 dB group. The data indicate that increasing sound stimulation causes a graded increase in the expression of calcium-binding protein immunoreactivity in the DCN and PVCN neurons and neuropil. This increase of protein expression is due to increased positive immunoreactivity in 'silent' neurons. These findings implicate that these neurons have the possibility to react against trauma and display calbindin or parvalbumin as a rescue event. The ability to map sound-induced calcium-binding protein changes in auditory neurons may be useful in future studies designed for detecting early patterns of neurodegeneration and neuroprotection in the central auditory pathway.

Quinine-induced hearing loss in the guinea pig is not affected by the Ca2+ channel antagonist verapamil.

It is well documented that quinine induces reversible hearing loss and tinnitus. The purpose in this study was to induce a quinine hearing loss and to investigate if verapamil, a Ca2+ channel antagonist of L-type might affect the response. Pigmented guinea pigs (n = 24) were anaesthetized by atropine. Hypnorm and midazolam but permitting spontaneous respiration. An electrode of platinum was placed on the round window and short (10 msec) tone pulses at 8 kHz were presented to the external ear. A typical deflection of the N1-wave was determined as the hearing threshold. Quinine hydrochloride 40 mg/kg and verapamil 1 mg/kg were given intravenously. Quinine induced a significant and reversible hearing loss (mean 16 dB). This hearing loss was not at all affected by verapamil given before or after quinine. Verapamil often caused acute cardiac arrest and particularly the combination verapamil followed by quinine-induced death to the animal. We conclude that verapamil and quinine had no in vivo interaction with regard to the hearing ability.

Effects of local anaesthetics on the gross receptor potentials in the guinea pig cochlea.

Local anaesthetics have been used intravenously and intratympanally to reduce tinnitus. In order to clarify its action in the periphery, we applied 0.5 mM tetracaine in the scala tympani in 18 cochleae and studied the effects on the receptor potentials. We used a temporal bone preparation of the guinea pig ear in vitro exposing the fourth cochlear turn where the cochlear microphonics (CM) and the summating potential (SP) were recorded. The perfusion was kept at a rate of 50 microliters/min. The frequency response of the cochlea was determined at the beginning of each experiment and the responses were recorded at the best frequency of the preparation. In another five cochleae an accumulated dose-response relationship was determined by increasing the tetracaine concentration in steps (50, 100, 300, 500, 1000 and 2000 microM), measuring the difference in amplitude of the receptor potentials. The CM decreased significantly (p < 0.001; mean 0.37 mV; SD 0.29). In 12 cochleae the SP was initially positive and did not increase significantly (p = 0.16; mean 0.07 mV; SD 0.16). In six cochleae the SP was initially negative and all changed polarity to positive and increased significantly (p < 0.05; mean 0.36 mV; SD 0.28). The effects on both the CM and the SP were reversible. Owing to the inter-individual variation between the cochleae the SP/CM ratio was determined and it increased significantly (p < 0.001; mean 0.18; SD 0.11). In the accumulated dose-response experiments the CM decreased significantly (p < 0.05) in a dose-dependent way, whereas the SP did not increase significantly. The SP/CM ratio increased significantly (p < 0.05) at 300 microM and 500 microM. We hypothesize that the peripheral tinnitus-reducing action of local anaesthetics is in part due to a reversal of the SP, but also to a reduction of the CM. The difference in effect of tetracaine on the receptor potentials, the CM and the SP, suggests that the SP is not dependent on the CM.

The concentration-effect relationship of quinine-induced hearing impairment.

Quinine-induced reversible hearing impairment at the frequencies of 1000 and 2000 Hz was investigated in healthy volunteers to analyze the plasma concentration-effect relationship of the drug. Six subjects were given two identical oral doses of quinine and a constant rate infusion of quinine over 6 hours (15 mg.kg-1) on three separate occasions. A simple pharmacodynamic model, E = k.C gamma (in which E is effect, k is a proportionality constant, C is drug concentration, and the exponent gamma is a fitting parameter), was found to describe well the relationship between hearing impairment and quinine concentrations in a hypothetical effect compartment. No statistical differences were found in the estimated parameters when the three dosings were compared, indicating that quinine-induced hearing impairment is independent of route of administration. The first-order rate constant (keo), linking plasma concentrations to the concentrations in the effect compartment, was (mean +/- SD) 0.71 +/- 0.19 and 0.99 +/- 0.37 hr-1 for 1000 and 2000 Hz, respectively. The corresponding values of k were 0.15 +/- 0.10 and 0.12 +/- 0.19 and the values of gamma were 2.13 +/- 0.57 and 3.44 +/- 1.04 for 1000 and 2000 Hz, respectively. Effect was also analyzed by semiparametric pharmacodynamic modeling, which gave results comparable to those obtained with the link model. We conclude that a simple power function is a reliable pharmacodynamic model for describing quinine-induced hearing impairment in healthy subjects.

[Frequency of induced abortions in mid-pregnancy at the Gynecology and Obstetrics Clinic in Sarajevo 1993-1994]. / Ucestalost prekida visokih trudnoca na Klinici za ginekologiju i akuserstvo u Sarajevu, u periodu 1993-1994. godine.

During the two war years, higher pregnancies were interrupted by 133 patients either for medical, social or ethical causes. To induce abortions, 15 methyl prostaglandin F2 was used. In advance, portions had been prepared (softened) with cervical application of prepidil gel in dose of 0.5 g. Starting eight to ten hours later Prostin 15 M was applied every 3 hours in dose of 250 mg. An average period from gel application to expulsion of ovulum was 30 hours by nullipara and 21 hours by patients who have delivered a child before. Due to strong uterotonic activity of these medicaments side effects like nausea, vomiting, diarrhoea and prostration occurred several times. Serious complications were registered in 4 patients. Three of them suffered cervix rupture due either to insufficient preparation or external orifitium spasm. The fourth one had profuse bleeding due to secondary atonia. Ruptures were sutured and bleeding stopped with standard uterotonic and blood transfusion.