Neurogenesis in the superior olivary complex in the rat

In a previous paper we provided evidence that crossed projection neurons are generated earlier than uncrossed projection neurons in the lateral superior olive. The aim of the present study was to determine if other major nuclei of the superior olivary complex (SOC), the medial superior olivary (MSO), the superior paraolivary (SPN) and the medial trapezoid (MTB) nuclei, are distinguished by their neuronal constitutions of birthdates. Pregnant rats were injected intraperitoneally with 5-bromodeoxyuridine (BrdU), the thymidine analogue, to label the neurons on one of the embryonic (E) days E11-E16. When the progeny rats reached adulthood, the brains were processed for BrdU immunohistochemistry. The MSO was mostly composed of neurons generated on E12 (95%). The remaining neurons in the MSO completed their neurogenesis by E13. The SPN neurons were generated from E12 to E14 with a peak on E13 (80%). Regardless of the morphological heterogeneity, the SPN consisted of a single population of neurons in terms of neurogenesis. The MTB neurons were generated from E13 to E16 with a peak on E14 (73%). In contrast to the previous assumption, no topographical relationship existed between neurogenesis and tonotopicity within each nucleus of the SOC.     

Chasing the dragon in the ear

In the UK, the prevalence of drug misuse has risen in the last decade. Otorhinolaryngological surgeons need to be aware that small amounts of illegal substances, such as heroin, cannabis and cocaine, may be hidden in the external auditory meatus. We report, for the first time, concealment of heroin in the external auditory meatus. The medico-legal and ethical considerations are also discussed.     

Temporal synchronization in the primary auditory response in the pigeon

Spike potentials were recorded from single fibres in the auditory nerve of the pigeon. In responses elicited by tonal stimuli, the timing of each spike relative to stimulus waveform was measured and period histograms were constructed. Phase locking of spikes was estimated in terms of a synchronicity index obtained by vector addition within the period histogram. A second measure of synchrony in the spike responses was obtained, that of temporal dispersion. For a population of fibres, vector strength of phase locking decreased for frequencies above 1 kHz, as reported for several other species. Temporal dispersion, however, also decreased with frequency, indicating enhanced temporal synchrony as frequency increased within the bandwidth of phase locking. The upper frequency limit of phase locking appears to depend on irreducible jitter of biological origin in the timing of spikes. For individual fibres, the bandwidth of synchronization of spikes consistently exceeds the response area, covering in addition the areas of suppression adjacent to the response area. Spike trains suppressed by a tonal stimulus become synchronized to that stimulus. Phase angles of synchronized responses systematically change as a function of tone level, when tone frequency is above or below CF, as reported for other avian species. Synchronicity and phase angle intensity functions are quite independent of spike rate intensity functions.     

Cation transport in the ampulla of the semicircular canal and in the endolymphatic sac

Summary We examined the effects of anoxia and ethacrynic acid on the endolymphatic potential and cation activity in the superior ampulla of the guinea pig, using double-barrelled ion-exchanger microelectrodes. In normal guinea pigs the ampullar endolymphatic potential was +3.9±1.2 mV (n=32), the Cl^– activity 130±4.6 mM (n=9), and the Na⁺ activity 18.4±4.4 mM (n=20). After anoxia, the ampullar DC potential decreased rapidly and reversed its polarity within 5 min. It then decreased gradually for 60 min and increased afterwards to approximately zero. K⁺ activity decreased gradually after a latency of 10 min, whereas Na⁺ activity increased. During the gradual decrease of a negative ampullar endolymphatic potential, an increase in Na⁺ activity was observed. Thirty minutes after the intravenous injection of ethacrynic acid (100 mg/kg), the potential began to decrease, changed to a negative polarity, and approached a maximum negative level 100 min after the injection. The decrease in K⁺ activity corresponded to the reduction of potential whereas Na⁺ activity remained unchanged. The DC potential of the endolymphatic sac in normal guinea pigs was + 14.7±5.1 mV (n=17). The Na⁺ concentration was 103.3±14.7 mM (n=14) and the K⁺ concentration was 11.6 ±0.8 mM (n=4). After anoxia, the DC potential decreased rapidly and approached 0 mV within 8 min. No negative potential could be observed. The Na⁺ concentration began to increase 2 min after anoxia and reached the extracellular Na⁺ concentration about 30 min later. No significant effect of intravenous administration of ethacrynic acid (100 mg/kg) on DC potential and Na + concentration could be observed. The results suggest the presence of a different ion transport system in the endolymphatic sac from that of the cochlea and the ampullae of the semicircular canals.     

Cation transport in the ampulla of the semicircular canal and in the endolymphatic sac

We examined the effects of anoxia and ethacrynic acid on the endolymphatic potential and cation activity in the superior ampulla of the guinea pig, using double-barrelled ion-exchanger microelectrodes. In normal guinea pigs the ampullar endolymphatic potential was + 3.9 +/- 1.2 mV (n = 32), the Cl- activity 130 +/- 4.6 mM (n = 9), and the Na+ activity 18.4 +/- 4.4 mM (n = 20). After anoxia, the ampullar DC potential decreased rapidly and reversed its polarity within 5 min. It then decreased gradually for 60 min and increased afterwards to approximately zero. K+ activity decreased gradually after a latency of 10 min, whereas Na+ activity increased. During the gradual decrease of a negative ampullar endolymphatic potential, an increase in Na+ activity was observed. Thirty minutes after the intravenous injection of ethacrynic acid (100 mg/kg), the potential began to decrease, changed to a negative polarity, and approached a maximum negative level 100 min after the injection. The decrease in K+ activity corresponded to the reduction of potential whereas Na+ activity remained unchanged. The DC potential of the endolymphatic sac in normal guinea pigs was + 14.7 +/- 5.1 mV (n = 17). The Na+ concentration was 103.3 +/- 14.7 mM (n = 14) and the K+ concentration was 11.6 +/- 0.8 mM (n = 4). After anoxia, the DC potential decreased rapidly and approached 0 mV within 8 min. No negative potential could be observed. The Na+ concentration began to increase 2 min after anoxia and reached the extracellular Na+ concentration about 30 min later.(ABSTRACT TRUNCATED AT 250 WORDS)     

A simple method for the demonstration of the bacterial spectrum in the nose and the nasopharynx in the infection-free interval in children with adenoid hypertrophy

The implications of bacterial colonization and distribution patterns in the nasopharynx and nasal cavities of children with adenoidal hypertrophy without clinical signs of acute infection are to be determined. We examined the spectrum and distribution of the facultative pathogenic bacterial flora in nasal cavities and nasopharynx of children with clinical apparent symptoms or signs of adenoid hypertrophy in an infection free interval. Compared with the nasal cavity we found an accumulation of pathogenic bacteria in the nasopharynx. A transnasal single swab from the nasopharynx showed to be the most effectively practical way to detect clinically relevant pathogenic bacteria. A thin flexible calcium-alginate swab was used in our experiments. Swabbing from the anterior nasal cavities proved to be a minor successful diagnostic method.     

Goblet cells in the laryngeal mucosa in cancer of the larynx

From 70 patients with laryngeal cancer, pieces of mucosa were taken from the subglottis, the entrance to the sinus of Morgagni, and from the ventricular fold. There were 35 taken at the time of diagnosis and the other 35 were taken after radiotherapy. By means of an elective staining method and a whole mount technique, morphological and quantitative studies of the goblet cells were performed. The findings were compared with corresponding investigations of goblet cells in normal larynges. The significantly lower density in the subglottis than in the sinus of Morgagni and ventricular fold observed in normal larynges was not found in the two groups of cancer patients. Instead, there was a tendency to an equalization of the goblet cell density in all 3 laryngeal regions. In the irradiated group the goblet cell density was lower, in all 3 regions, than in the nonirradiated cancer group and in normal larynges. In the close vicinity of the cancer the goblet cell density was reduced, possibly because the cancer process had initiated metaplasia to an epithelium which was poor in goblet cells. Between the two cancer groups and normal larynges there were no morphological differences in the goblet cells.     

Firing mechanisms in the single vestibular neurons in the cat.

Spontaneous unitary discharges in nucleus vestibularis lateralis (NVL) neurons were studied in locally anesthetized cats. The mean +/-S.E. firing rate of spontaneous unitary discharges of NVL neurons was 19.8 +/- 0.9 Hz. About 12% of NVL neurons showed a random firing. The spontaneous unitary discharge rate of the gamma distribution at lambda=2 was relativley low. However, the others were high. Patterns of peak interval time of the distribution with one peak and the interpeak interval time of those with two and three peaks were almost the same.