In vitro TRH release from hypothalamus slices varies during the diurnal cycle

We have previously described a daily rhythm in thyrotropin releasing hormone (TRH) and TRH mRNA in the rat hypothalamus. To determine whether TRH release fluctuates in a diurnal manner, we have measured basal and potassium stimulated release from hypothalamic slices, and compared it to release from olfactory bulb slices, during the diurnal cycle. Basal TRH release was higher at 7:00 h than at any other time (1:00, 13:00 or 19:00 h) in either hypothalamus or olfactory bulb. The ratio of stimulated over basal release was higher in the hypothalamus at 19:00 h, when TRH content was highest. Potassium stimulated TRH release from olfactory bulb was not different from basal release at any time. TRH release fluctuations were not due to a rhythm of extracellular inactivation: the activity of pyroglutamyl aminopeptidase II, an ectoenzyme responsible for TRH inactivation, was constant throughout the cycle. Our data demonstrate that diurnal variations of TRH release occur in vitro and that the enhanced responsiveness to potassium stimulation in hypothalamus is correlated with increased levels of peptide.     

Phylogeny of Greya (Lepidoptera: Prodoxidae), based on nucleotide sequence variation in mitochondrial cytochrome oxidase I and II: congruence with morphological data

The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from nucleotide sequence variation across a 765-bp region in the cytochrome oxidase I and II genes of the mitochondrial genome. Most parsimonious relationships of 25 haplotypes from 16 Greya species and two outgroup genera (Tetragma and Prodoxus) showed substantial congruence with the species relationships indicated by morphological variation. Differences between mitochondrial and morphological trees were found primarily in the positions of two species, G. variabilis and G. pectinifera, and in the branching order of the three major species groups in the genus. Conflicts between the data sets were examined by comparing levels of homoplasy in characters supporting alternative hypotheses. The phylogeny of Greya species suggests that host-plant association at the family level and larval feeding mode are conservative characters. Transition/transversion ratios estimated by reconstruction of nucleotide substitutions on the phylogeny had a range of 2.0-9.3, when different subsets of the phylogeny were used. The decline of this ratio with the increase in maximum sequence divergence among taxa indicates that transitions are masked by transversions along deeper internodes or long branches of the phylogeny. Among transitions, substitutions of A-->G and T-->C outnumbered their reciprocal substitutions by 2-6 times, presumably because of the approximately 4:1 (77%) A+T-bias in nucleotide base composition. Of all transversions, 73%-80% were A<-->T substitutions, 85% of which occurred at third positions of codons; these estimates did not decrease with an increase in maximum sequence divergence of taxa included in the analysis. The high frequency of A<-->T substitutions is either a reflection or an explanation of the 92% A+T bias at third codon positions.      

Early stages of vocal ontogeny in the magpie (Pica pica)

Summary The vocal repertoire of magpie (Pica pica) chicks consists of six calls: Begging Trill (BT), Soft Whistle (SW), Begging Scream (BS), Alarm Call (AC), Distress Call (DC) and Brief Contact Note (BCN). Both BT and SW have a tonal structure and their occurrence is restricted to the nestling period. At fledging, there is a gradual change from BT into BS and a sudden appearance of harsh calls similar to those of adult birds (AC, DC, BCN), without evident transitional forms with preceding tonal calls. Both the existence and the structural design of calls seem to be adapted for providing nestlings with immediate benefits linked to the two major chapters of allocation of parental care. Emission rates of BT increase with hunger motivation under laboratory conditions. Their structure suggests that they are easily located but liable to suffer from environmental degradation. BS of fledglings may be more resistant to degradation, a trait which may facilitate the identification by parents of their own offspring. Both AC and DC attract parents to defend the nest against potential predators, and their structure make them to be easily located and detectable at long distances. BCN are given by fledglings during bouts of locomotory activity (exploration and play) and they probably help in maintaining the cohesion of the group under conditions of poor visibility. In accordance, this call may be fairly located at short distances. The function of SW was unclear. It is given during periods of nestling inactivity between begging bouts, and could be easily elicited by tactile and auditory stimuli. After laboratory experiments, it is concluded that SW serve to indicate parents that nestlings are in good condition, hence to benefit from the parental willingness to invest in a brood with high prospects of survival. Since (i) there is a widespread lack of continuity in the development of adult vocalizations starting from nestling calls, and (ii) nestling calls seem to have evolved to provide birds with benefits in the short-term, these facts argue against the prevailing idea that the main function of calls early in ontogeny is to act as precursors of adult vocalizations.

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Zusammenfassung Das Lautrepertoire von Elsternestlingen besteht aus 6 Lautäußerungen: Betteltrillern (BT), Sanftes Pfeifen (SP), Bettelkreischen (BK), Alarmruf (AR), Angstschreien (AS) und kurzer Kontaktruf (KR). BT und SP sind tonal und treten nur während der Nestlingsperiode auf. Zum Zeitpunkt des Ausfliegens geht BT graduell in BK über und plötzlich treten auch ohne vorausgehende tonale Übergangsformen rauhe Rufe ähnlich denen der Altvögel auf (AR, AS, KR). Sowohl die Existenz als auch die Struktur der Lautäußerungen scheinen als Anpassungen im Zusammenhang mit einer Optimierung der Brutpflege zu interpretieren zu sein. Die Emissionsrate von BT steigt unter Laborbedingungen mit der Hungermotivation. Die Struktur legt nahe, daß BT leicht geortet werden kann, aber auch leicht von der Umgebung verschluckt wird. BS der flüggen Jungen scheint davon weniger betroffen zu sein, so daß die Eltern leichter ihre Jungen identifizieren können. AR und AS veranlassen die Altvögel, ihr Nest gegenüber potentiellen Prädatoren zu verteidigen; die Struktur der Laute begünstigt ihre Ortung und Wahrnehmung über größere Entfernungen. KR werden von den flüggen Jungen bei lebhafter lokomotorischer Aktivität (Exploration, Spiel) geäußert; sie tragen vielleicht dazu bei, die Gruppe auch unter erschwerten optischen Kontaktmöglichkeiten zusammenzuhalten. Die Funktion von SP blieb unklar. SP war während inaktiver Perioden zwischen Bettelverhalten zu hören und konnte leicht durch taktile und akustische Reize ausgelöst werden. Nach Laborexperimenten ist zu schließen, daß SP den Eltern Wohlbefinden der Jungen anzeigt und so Bereitschaft zur Investition in eine Brut mit hoher Überlebenswahrscheinlichkeit fördert. Daß (1) zwischen den Rufen der Altvögel und dem Repertoire der Nestlingen weitgehend keine kontinuierlichen Übergänge festzustellen und (2) Nestlingsrufe offensichtlich im Hinblick auf kuzfristige Gewinne zu interpretieren sind, spricht gegen die allgemein vorherrschende Ansicht, das Lautrepertoire in frühen Stadien der Ontogenie sei hauptsächlich ein Vorläufer der Adultlaute.