The role of leaders in intracellular transport and secretion of the insulin precursor in the yeast Saccharomyces cerevisiae.

Pulse-chase analysis of folded and misfolded insulin precursor (IP) expressed in Saccharomyces cerevisiae was performed to establish the requirements for intracellular transport and the influence of the secretory pathway quality control mechanisms on secretion. Metabolic labelling of the IP expressed in S. cerevisiae showed that the effect of a leader was to stabilise the IP in the endoplasmic reticulum (ER), and facilitate intracellular transport of the fusion protein and rapid secretion. The first metabolically labelled IP appeared in the culture supernatant within 2-4 min of chase, and most of the secreted IP appeared within the first 15 min of chase. After enzymatic removal of the leader in a late Golgi apparatus compartment, the IP followed one of two routes: (1) to the plasma membrane and hence to the culture supernatant, or (2) to a Golgi or post-Golgi compartment from which secretion was restricted. Combined secretion and intracellular retention of the IP reflected either saturation of a Golgi or post-Golgi compartment and secretion as a consequence of overexpression, or competition between secretion and intracellular retention. IP which was misfolded, either due to amino acid substitution or because disulphide bond formation had been prevented with dithiothreitol (DTT), was transported from the ER to the Golgi apparatus but then retained in a Golgi or post-Golgi compartment and not exported to the culture supernatant.     

Ultrastructural Observations on the Epidermis of Xenoturbella bocki Westblad, 1949; With a Discussion of Epidermal Cytoplasmic Filament Systems of Invertebrates

The highly complex epidermis of Xenoturbella bocki has been studied, mainly employing transmission electron microscopical and histochemical methods. The epidermal organization is described to best advantage in terms of the various cell types present, their intricate interrelationships and their interaction with the highly developed subepidermal membrane complex (SMC). The epidermis is composed mainly of ciliated epidermal supporting cells, at least two types of gland cells (one dominant mucous type with basophilic, alcian blue-positive granules; another possessing acidophilic, PAS-positive granules), several types of nerve cells present in the intraepidermal nerve layer and, finally, some peculiar basally arranged 'pillow cells'. Junctional structures are sparsely developed. The epidermal supporting cell is provided with a distinct cell web, but diagnostic for this cell type is the presence of a very prominent single supporting fibre (SF) composed of supporting filaments. Distally some of these filaments may terminate on the tapering proximal ends of ciliary rootlets, a highly unusual phenomenon. Basally the SF is attached to the SMC in a complex arrangement. The possible relationship of the supporting filaments to cytoskeletal intermediate filaments is discussed. The SF is compared to other cytoplasmic filament systems in mammals and various invertebrates. The ultrastructural organization of Xenoturbella is now fairly well understood, nevertheless, our conclusion must be that it is still not possible to assign an appropriate place for this animal in the systematic-phylogenetic system.     

Temporal relationships between shock treatment and intermale fighting behaviour in laboratory mice. Effects of modifying testicular and adrenal functions

The three experiments of this series were conducted to (1) examine subsequent effects of electric shock on intermale fighting in previously isolated mice, and (2) determine to what extent post-shock fighting is affected by manipulations of the pituitary-gonadal and pituitary-adrenocortical axes. In experiment 1 it was found that shock treatment significantly increases fighting $\text{1}\text{2}$ to 1 h later. Experiment 2 showed that castration alone does not affect post-shock fighting, whereas adrenalectomy and castration combined with adrenalectomy both inhibit such fighting. Experiment 3 showed that pretreatment with testosterone increases fighting in intact males, but fails to restore post-shock fighting in adrenalectomized and castrated-adrenalectomized males. These findings suggest that (1) the pituitary-adrenocortical axis plays an important role in controlling post-shock fighting in mice, and (2) the inhibition of post-shock fighting by adrenalectomy and castration combined with adrenalectomy is not a result of the loss of adrenal testosterone which accompanies these operations.     

Age-dependent changes in the number of [3H]ouabain-binding sites in rat soleus muscle

The influence of age on the number of (Na+K+)-ATPase units in skeletal muscle has been assessed by measurements of [3H]ouabain binding in vitro and in vivo to rat soleus muscle. In vitro measurements showed that from the 2nd to the 28th day of life, the number of [3H]ouabain-binding sites increases from 120 to 580 pmol/g wet wt. This is followed by a decrease, until a plateau between 150 and 200 pmol/g is reached around 150 days after birth. 60 min after intraperitoneal injection of [3H]ouabain (12.5 mumol/kg body weight), the soleus muscles of 28-day-old rats had accumulated 2.4-times more 3H-activity per g wet wt. than muscles of 85-day-old rats and the 3H-activity in plasma was 54% lower. The results may explain the low sensitivity to digitalis glycosides found in infants as compared to premature or adult individuals.     

A molecular phylogeny of minivets (Passeriformes: Campephagidae: Pericrocotus): implications for biogeography and convergent plumage evolution

Jønsson, K. A., Irestedt, M., Ericson, P. G. P. & Fjeldså, J. (2009). A molecular phylogeny of minivets (Passeriformes: Campephagidae: Pericrocotus ): implications for biogeography and convergent plumage evolution.— Zoologica Scripta, 39 , 1–8.
Minivets are conspicuous and mostly intensely colourful birds inhabiting wooded environments in tropical and subtropical South and Southeast Asia and temperate East Asia. We present a robust phylogeny of the group based on nuclear and mitochondrial DNA data including all 12 recognized species and also many subspecies representing disjunct populations in the Oriental mainland and in Indonesia. The study indicates that minivets radiated within mainland Asia and dispersed to the Indonesian archipelago. We also demonstrate that in accordance with studies on other bird groups, plumage characters are highly plastic and that the diversity of plumage patterns and colouration represents an example of convergent evolution.     

Effects of repeated exposure to electric footshock on subsequent agonistic behaviour and adrenocortical secretion in male mice of different androgen status

Two experiments were conducted to examine effects of repeated exposure to electric footshock on subsequent agonistic behaviour and adrenocortical secretion in male mice of different androgen status. Aggressive and submissive behavioural components were independently studied in the two experiments. It was found that repetition reduced aggressive, and stimulated submissive and adrenocortical responses to shock, particularly in castrates. The direction of the shock effects on aggressive behaviour was reversed by repetition in castrates, whereas only the magnitude of the behavioural responses was changed at normal androgen levels. It is suggested that the changes in agonistic responses to shock induced by repetition are mediated by changes in pituitary-adrenocortical secretion, and that androgen inhibits the shock effects on agonistic behaviour through inhibition of the pituitary-adrenocortical responses to shock.