Brain stem and inner ear abnormalities in children with auditory neuropathy spectrum disorder and cochlear nerve deficiency.

BACKGROUND AND PURPOSE: Cranial abnormalities, including CND, are common in children with ANSD. The purpose of this study was to assess whether CND is associated with brain or inner ear abnormalities in a cohort of children with ANSD. MATERIALS AND METHODS: Two neuroradiologists retrospectively reviewed cranial MR imaging examinations in 103 children with ANSD. Brain, cochlear nerve, and temporal bone abnormalities were described and tabulated. Findings were stratified on the basis of the presence and laterality of CND, and differences in the presence of associated inner ear or intracranial abnormalities were assessed by using 2-tailed Fisher exact tests. RESULTS: CND was identified in 33.0% of children and 26.9% of ears with ANSD. Significantly more patients with bilateral CND had intracranial abnormalities than those with unilateral CND (60.0% versus 15.8%; P = .012). Forty percent of patients with bilateral CND, 0% of patients with unilateral CND, and 10.1% of those without CND demonstrated hindbrain malformations. Patients with bilateral CND were more likely to demonstrate hindbrain malformations than patients with normal nerves (P = .01) or unilateral CND (P = .004). Labyrinthine abnormalities were significantly more common in patients with bilateral CND than in those without CND (P ≤ .001). Cochlear anomalies were more common in patients with bilateral versus unilateral CND (P = .01). IAC and cochlear aperture stenosis were more common in those with unilateral and bilateral CND than those without CND (both P < .001). CONCLUSIONS: Cochlear and hindbrain abnormalities are significantly more common among patients with ANSD with bilateral CND compared with those with at least 1 intact cochlear nerve.

Identification of subtypes of muscarinic receptors that regulate Ca2+ and K+ channel activity in sympathetic neurons.

Many different G protein-coupled receptors modulate the activity of Ca2+ and K+ channels in a variety of neuronal types. There are five known subtypes (M1-M5) of muscarinic acetylcholine receptors. Knockout mice lacking the M1, M2, or M4 subtypes are studied to determine which receptors mediate modulation of voltage-gated Ca2+ channels in mouse sympathetic neurons. In these cells, muscarinic agonists modulate N- and L-type Ca2+ channels and the M-type K+ channel through two distinct, G-protein mediated pathways. The fast and voltage-dependent pathway is lacking in the M2 receptor knockout mice. The slow and voltage-independent pathway is absent in the M1 receptor knockout mice. Neither pathway is affected in the M4 receptor knockout mice. Muscarinic modulation of the M current is absent in the M1 receptor knockout mice, and can be reconstituted in a heterologous expression system using cloned channels and M1 receptors. Our results using knockout mice are compared with pharmacological data in the rat.

Reconstitution of muscarinic modulation of the KCNQ2/KCNQ3 K(+) channels that underlie the neuronal M current.

Channels from KCNQ2 and KCNQ3 genes have been suggested to underlie the neuronal M-type K(+) current. The M current is modulated by muscarinic agonists via G-proteins and an unidentified diffusible cytoplasmic messenger. Using whole-cell clamp, we studied tsA-201 cells in which cloned KCNQ2/KCNQ3 channels were coexpressed with M(1) muscarinic receptors. Heteromeric KCNQ2/KCNQ3 currents were modulated by the muscarinic agonist oxotremorine-M (oxo-M) in a manner having all of the characteristics of modulation of native M current in sympathetic neurons. Oxo-M also produced obvious intracellular Ca(2+) transients, observed by using indo-1 fluorescence. However, modulation of the current remained strong even when Ca(2+) signals were abolished by the combined use of strong intracellular Ca(2+) buffers, an inhibitor of IP(3) receptors, and thapsigargin to deplete Ca(2+) stores. Muscarinic modulation was not blocked by staurosporine, a broad-spectrum protein kinase inhibitor, arguing against involvement of protein kinases. The modulation was not associated with a shift in the voltage dependence of channel activation. Homomeric KCNQ2 and KCNQ3 channels also expressed well and were modulated individually by oxo-M, suggesting that the motifs for modulation are present on both channel subtypes. Homomeric KCNQ2 and KCNQ3 currents were blocked, respectively, at very low and at high concentrations of tetraethylammonium ion. Finally, when KCNQ2 subunits were overexpressed by intranuclear DNA injection in sympathetic neurons, total M current was fully modulated by the endogenous neuronal muscarinic signaling mechanism. Our data further rule out Ca(2+) as the diffusible messenger. The reconstitution of muscarinic modulation of the M current that uses cloned components should facilitate the elucidation of the muscarinic signaling mechanism.

A mutation in the second transmembrane region of the CB1 receptor selectively disrupts G protein signaling and prevents receptor internalization.

We mutated a conserved aspartate in the second transmembrane domain of the cannabinoid CB(1) receptor to asparagine (D164N), stably transfected it into AtT20 cells, and examined the coupling of this mutant receptor to several intracellular effectors that are targets of wild-type CB(1) receptor activation. We found that the D164N receptor binds the CB(1) agonist WIN 55,212-2 with an affinity matching that of the wild-type CB(1) receptor and inhibits Ca(2+) currents and cAMP production with an equivalent potency and efficacy. This mutation, however, blocks coupling of the receptor to the potentiation of inwardly rectifying potassium channel (KIR) currents and prevents internalization of the receptor after exposure to agonist. Although the mutant receptor did not internalize, we found it was still capable of activating p42/44 MAP kinase. In addition, we made a reciprocal mutation that exchanged the aspartate with an asparagine in the seventh transmembrane region (D164N/N394D). In other seven-membrane-spanning receptors, this reciprocal mutation is known to restore functions disrupted by the mutation of the single conserved aspartate. However, activation of D164N/N394D did not potentiate KIR current, nor did it internalize. We conclude that D164 is necessary for potentiation of KIR current and internalization of receptor but not necessary for agonist binding, inhibition of cAMP production, inhibition of Ca(2+) currents, or activation of p42/44 MAP kinase. Furthermore, CB(1) receptor internalization is not necessary for MAP kinase activation.

Distinct domains of the CB1 cannabinoid receptor mediate desensitization and internalization.

Desensitization of cannabinoid receptor signaling by a G-protein coupled receptor kinase (GRK) was examined using the Xenopus oocyte expression system. Application of a CB1 agonist, WIN 55,212-2, evoked a concentration-dependent increase in K+ conductance (Kir3) in oocytes coexpressing rat CB1 with the G-protein-gated, inwardly rectifying K+ channels Kir3.1 and Kir3.4. Desensitization was slight during continuous agonist application in the absence of GRK and arrestin. However, coexpression of GRK3 and beta-arrestin 2 (beta-arr2) caused profound homologous CB1 receptor desensitization, supporting the hypothesis that GRK3 and beta-arr2 effectively produce CB1 receptor desensitization. To identify the regions of the CB1 receptor responsible for GRK3- and beta-arr2-mediated desensitization, we constructed several CB1 receptor mutants. Truncation of the C-terminal tail of CB1 receptor at residue 418 (Delta418) almost completely abolished desensitization but did not affect agonist activation of Kir3. In contrast, truncation at residues 439 and 460 did not significantly affect GRK3- and beta-arr2-dependent desensitization. A deletion mutant (Delta418-439) did not desensitize, indicating that residues within this region are important for GRK3- and beta-arr2-mediated desensitization. Phosphorylation in this region was likely involved in desensitization, because mutation of either of two putative phosphorylation sites (S426A or S430A) significantly attenuated desensitization. CB1 receptors rapidly internalize after activation by agonist. Phosphorylation of S426 or S430 was not necessary for internalization, because the S426A/S430A CB1 mutant internalized when stably expressed in AtT20 cells. These studies establish that CB1 desensitization can be regulated by a GRK and that different receptor domains are involved in GRK- and beta-arrestin-dependent desensitization and CB1 internalization.

Ca2+ channel beta3 subunit enhances voltage-dependent relief of G-protein inhibition induced by muscarinic receptor activation and Gbetagamma.

The Ca2+ channel beta subunit has been shown to reduce the magnitude of G-protein inhibition of Ca2+ channels. However, neither the specificity of this action to different forms of G-protein inhibition nor the mechanism underlying this reduction in response is known. We have reported previously that coexpression of the Ca2+ channel beta3 subunit causes M2 muscarinic receptor-mediated inhibition of alpha1B Ca2+ currents to become more voltage-dependent. We report here that the beta3 subunit increases the rate of relief of inhibition produced by a depolarizing prepulse and also shifts the voltage dependency of this relief to more hyperpolarized voltages; these effects are likely to be responsible for the reduction of inhibitory response of alpha1B channels to G-protein-mediated inhibition seen after coexpression of the Ca2+ channel beta3 subunit. Additionally, the beta3 subunit alters the rate and voltage dependency of relief of the inhibition produced by coexpressed Gbeta1gamma1, in a manner similar to the changes it produces in relief of M2 receptor-induced inhibition. We conclude that the Ca2+ channel beta3 subunit reduces the magnitude of G-protein inhibition of alpha1B Ca2+ channels by enhancing the rate of dissociation of the G-protein betagamma subunit from the Ca2+ channel alpha1B subunit.

The Ca2+ channel beta3 subunit differentially modulates G-protein sensitivity of alpha1A and alpha1B Ca2+ channels.

We have shown previously that the Ca2+ channel beta3 subunit is capable of modulating tonic G-protein inhibition of alpha1A and alpha1B Ca2+ channels expressed in oocytes. Here we determine the modulatory effect of the Ca2+ channel beta3 subunit on M2 muscarinic receptor-activated G-protein inhibition and whether the beta3 subunit modulates the G-protein sensitivity of alpha1A and alpha1B currents equivalently. To compare the relative inhibition by muscarinic activation, we have used successive ACh applications to remove the large tonic inhibition of these channels. We show that the resulting rebound potentiation results entirely from the loss of tonic G-protein inhibition; although the currents are temporarily relieved of tonic inhibition, they are still capable of undergoing inhibition through the muscarinic pathway. Using this rebound protocol, we demonstrate that the inhibition of peak current amplitude produced by M2 receptor activation is similar for alpha1A and alpha1B calcium currents. However, the contribution of the voltage-dependent component of inhibition, characterized by reduced inhibition at very depolarized voltage steps and the relief of inhibition by depolarizing prepulses, was slightly greater for the alpha1B current than for the alpha1A current. After co-expression of the beta3 subunit, the sensitivity to M2 receptor-induced G-protein inhibition was reduced for both alpha1A and alpha1B currents; however, the reduction was significantly greater for alpha1A currents. Additionally, the difference in the voltage dependence of inhibition of alpha1A and alpha1B currents was heightened after co-expression of the Ca2+ channel beta3 subunit. Such differential modulation of sensitivity to G-protein modulation may be important for fine tuning release in neurons that contain both of these Ca2+ channels.

Courtship bout duration in per circadian period mutants in Drosophila melanogaster.

Mutations on the period locus of Drosophila melanogaster influence circadian periods as well as the rhythm in inter-pulse intervals in male courtship song; perL mutations produce long circadian periods and courtship song rhythms and per(s) mutations produce short circadian periods and courtship song rhythms. Thus, these mutations influence timing mechanisms over both long and short behavioral time horizons. We examined if the mean courtship duration of male Drosophila melanogaster cycles rhythmically, and if mutations at the period locus influence courtship bout duration. We measured the courtship bout durations of the following: (1) wild type Canton-S (per+) males; (2) perL males; and (3)per(s) males. Rhythmicity of courtship bout duration could not be mathematically determined. Mean courtship bout duration did not differ among the three groups; thus, mutations at the period locus did not influence mean courtship duration. There was a nonsignificant trend for per+ males that were successful at mating to have longer mean courtship duration than unsuccessful males.

The influence of current-visit experience within a prey patch on patch persistence.

A critical component of efficient foraging behavior is leaving a feeding site when prey density in that site declines. If ``real time'' hypotheses are to explain patch-leaving mechanisms, we will need to examine the influence that moment-to-moment experience within a current prey patch has on persistence in that patch. We used linear regression to investigate how current experience of patch quality influenced homing pigeons' patch persistence. We did this by examining the amount of variance in persistence that was accounted for by different measures of within-session patch quality. The importance of several measures of the precise sequence of events in individual sessions were assessed with selected averaging algorithms. Mean inter-capture interval and mean number of inter-capture pecks accounted for a significant amount of the variance in giving-up time in three of four, and four of four birds, respectively. Conversely, only one rate measure in one bird showed an influence on patch persistence. In three birds, recent information had a strong influence on giving-up time. Current-visit experience did influence the patch persistence of the pigeons, but the birds' behavior indicated that different individuals used different measures of patch quality, different mechanisms of assessing those measures, and different patch-exit mechanisms.

Abolition of G protein inhibition of alpha 1A and alpha 1B calcium channels by co-expression of the beta 3 subunit.

Three different classes of alpha 1 Ca2+ channel (alpha 1A, alpha 1B, alpha 1C) were expressed in Xenopus oocytes to determine whether G protein-mediated inhibition is an inherent property of the alpha 1 subunit itself, and if so, whether co-expression of auxiliary subunits modulates the inhibition seen. From our data it is apparent that either alpha 1A or alpha 1B Ca2+ channels expressed alone are sufficient for voltage-dependent G protein inhibition. alpha 1C Ca2+ channels expressed alone do not exhibit the G protein inhibition seen in alpha 1A and alpha 1B channels. Additionally, co-expression of the beta 3 subunit abolishes the ability of G proteins to inhibit currents through alpha 1A and alpha 1B Ca2+ channels. Differential sensitivity of alpha 1 as well as modulation of properties by beta 3 provide a potential mechanism for the regulation of G protein-mediated inhibition in neurons.

Premarital sexuality: a five-year follow-up study of attitudes and behavior by dating stage.

This paper presents the results of a survey on premarital sex conducted in 1988. The study focused on what respondents considered proper sexual behavior, what they reported they did, and what they thought others were doing at five stages of dating. Respondents were asked about cohabitation, the effect of AIDS on their premarital attitudes and behavior, and their views regarding the morality of premarital sex. When compared to the results of a similar study conducted in 1983, the data provided some evidence of change in premarital sexual attitudes and behavior. Female respondents in the 1988 sample showed lower levels of sexual intercourse at all five dating stages than did their counterparts in the 1983 study. However, males in the 1988 sample reported higher levels of sexual intercourse for the first four stages of dating than did males in the 1983 survey. In general, both males and females in the 1988 sample reported changing their attitudes and behavior regarding premarital sex in the direction of greater conservatism since hearing about AIDS. Attitudinal change was more widespread than actual behavioral change.

A case of amiodarone-induced hyperthyroidism and hepatitis: results of clinical laboratory and histological tests.

We report a case of amiodarone-induced hepatitis accompanied by hyperthyroidism in which estimations of amiodarone in blood and in the liver and histological examinations were performed at the start and end of a 3-month interval. Our observation demonstrates the persistence in the liver of amiodarone and its principal metabolite for 3 months after the drug was withdrawn. There was no correlation between the persistence of the drug, the elevation of enzyme levels, and the extent of histological damage in the liver.

Premarital sex: attitudes and behavior by dating stage.

Using data gathered from a sixty-three item dating and mate-selection questionnaire completed by two hundred and eighty student and nonstudent respondents, this study investigates the differences between what people believe is proper premarital sexual behavior, what they do and what they think others are doing at five stages of dating. It was found that persons are most restrictive in what they believe is proper conduct, more permissive in their reported behavior, and most permissive in their perception of what others are doing. During the early stages of dating, males and females differ widely in their outlook as to what is proper behavior and also in their reported behavior. Other studies which failed to take dating stage into consideration may have missed important gender differences in the early period of dating.

PIP: Using data gathered from a 63-item dating and mate-selection questionnaire completed by 280 student and nonstudent respondents, in Southern New England, US, this study investigates the differences between what people believe is proper premarital sexual behavior, and what they think others are doing at 5 stages of dating. It was inspired by the suggestions of several other studies and general observations: that young people in the 1980s are more conservative in their general outlook, and possibly also in regards to premarital sex behavior. Another purpose was to examine the influence of social factors such as age, gender, religion, mother's education, father's education, residence, and religiosity. The sample consisted of college students from a state college and college-age youths. Behaviors were placed in categories ranged from the least to the most intimate. There is an increase in permissiveness for both males and females at each successive stage, with females most likely to engage in sexual intimacy in the committed stages of a relationship. Differences between male and female attitudes disappear towards later stages. It was found that persons are most restrictive in what they believe is proper conduct, more permissive in their reported behavior, and most permissive in their perception of what others are doing: there is a pull from the reference group in favor of permissiveness. Analysis of the data indicates there is a much higher level of sexual activity than in the 1950s and 60s. 3 factors: gender, religiosity, and religious attendance were found to make statistically significant differences to the dependent variables. Other studies which failed to take dating stage into consideration may have missed important gender differences in the early period of dating.