Seasonal variation in the diet of the king penguin (Aptenodytes patagonicus) at sub-Antarctic Marion Island

King penguins are important consumers of marine resources, throughout the year, at the Prince Edward Islands. Meal size varied from 8.5–12.6% of adult mass, depending on the method of determination. In spite of the biases in the analysis favouring the overestimation of squid, fish and, in particular, myctophid fish accounted for the largest proportion of the stomach samples, 87% by wet mass, 75% by numbers and 69% by reconstituted mass. The relative abundance of fish in the diet dropped markedly in winter followed by a subsequent rise to nearly 100% in summer. This rise coincided with an increase in the chick growth rate and the king penguin population at the island and suggests the rise in relative abundance offish reflects a real increase in the availability of fish around the islands.
Juvenile and adult Krefftichthys anderssoni/Protomyctophum tenisoni and adult Electrona carlsbergi were the most common fish consumed. There was an increase in the modal size of K. anderssoni/P. tenisoni throughout the year which we interpret as growth of a single fish population. Juvenile Kondakoviu longimana was the important squid species taken by king penguins. Crustaceans were only rarely recorded in the diet and may have come from digestion of fish and squid stomachs.
This is the first study of the diet of a Southern Ocean pelagic predator that has identified myctophid fish as a major component of its diet. All three important fish species taken by king penguins at Marion Island have a wide distribution throughout the Southern Ocean and consequently may prove to be important dietary components of other Southern Ocean pelagic predators.     

Interactions of three sequentially expressed genes control temporal and spatial specificity in Aspergillus development

Aspergillus nidulans brlA, abaA, and wetA form a dependent pathway that regulates asexual reproductive development. The order in which these genes are expressed determines the outcome of development. Expression of brlA in vegetative cells leads to activation of abaA and wetA, cessation of vegetative growth, cellular vacuolization, and spore formation. By contrast, expression of abaA in vegetative cells does not result in conidial differentiation but does lead to activation of brlA and wetA, cessation of vegetative growth, and accentuated cellular vacuolization. brlA, abaA, and wetA act individually and together to regulate their own expression and that of numerous other sporulation-specific genes. We propose that the central pathway controlling development is largely autoregulatory. The timing and extent of expression of the regulatory genes and their targets are determined as development proceeds by intrinsically controlled changes in the relative concentrations of regulatory gene products in the various conidiophore cell types.     

Mouse DNA methylase. Intracellular location and degradation

DNA methylase extracted with low salt from mouse Krebs II ascites cell nuclei has been degraded stepwise by trypsin treatment. Degradation, accompanied by a limited reduction in size of the native enzyme, leads to the progressive introduction of several nicks so that, eventually, fragments of 14, 18, 24 and 28 kD are released on denaturation. This illustrates the domain structure of the enzyme. In contrast to ascites cell nuclear extracts, preparations from liver nuclei are already nicked and the major from of the enzyme contains a 100 kD fragment though the native molecular weight is unchanged. Newborn mouse liver contains more undegraded enzyme that is mostly firmly-bound within the nucleus. Trypsin treatment increases the de novo activity of the enzyme and prevents its aggregation in the absence of salt, even in the presence of high concentrations of native DNA.     

Superoxide dismutase inhibition of alkaline hemin-mediated O2 activation

Inhibition of hemin-mediated O2 activation by bovine superoxide dismutase and the copper tetrammine complex has been examined. It is shown that the inhibitory effect of these species is not due to metabolism of O2-., but to a nonspecific inhibition of the process by the Cu2+ ion. We propose that the inhibition occurs at the level of electron transfer from NADH to iron in an analogous manner to that proposed for the Cu2+ inhibition of microsomal electron transfer.     

Immunocytochemical detection of prolactin or prolactin-like immunoreactivity in epididymis of mature male mouse

Summary Prolactin (PRL) binds to the testis of mice and rats where it increases the number of luteinizing hormone receptors, increases the binding of human chorionic gonadotropin (hCG) to LH receptors, and enhances testosterone synthesis and secretion. PRL also binds to the prostate and seminal vesicles of rats and humans where it increases organ weight and stimulates growth and uptake of testosterone. PRL binds to the epididymis of rats but the effect of PRL on this organ is unknown. In the present study, a standard immunoperoxidase (PAP) technique was used to detect the binding of endogenous and exogenous PRL or PRL-like peptides to the epididymis of the mature mouse. Throughout the epididymal duct, a positive reaction for peroxidase, suggesting PRL or PRL-like binding, occurred in the Golgi area of principal cells. In segment 1, positive reactions were also visualized in the perinuclear area and in the region located between the Golgi area and the apical surface of the principal cells (supra-Golgi area). In the corpus and cauda epididymidis, scattered entire principal cells were also positive. Throughout the epididymal duct, the reactions indicating the binding of exogenous PRL were slightly stronger than those testing for binding of endogenous peptides. The significance of such binding to the epididymis is uncertain but PRL may perform the same functions in epididymal principal cells as it does in the testis, prostate, and seminal vesicles.     

Persistent sympathetic nervous system arousal associated with tethering in cynomolgus macaques

The swivel-tether system has been used extensively in biomedical research involving nonhuman primates, yet there has been little or no investigation into potential adverse influences of this form of restraint on research results. In the study described here, a portable electrocardiographic telemetry system was used for continuous monitoring of the heart rate of 26 cynomolgus monkeys while: (a) pair-caged, 8 weeks prior to tethering; (b) singly-caged, tethered; (c) singly-caged, tethered, administered propranolol (30 mg/kg/day) in the diet; (d) group-housed (five monkeys per group), 1 week after group formation; and (e) group-housed (five monkeys per group), 4 weeks after group formation. Tethering resulted in persistent elevations in heart rate relative to the other conditions. Administration of propranolol, a beta-adrenergic antagonist, resulted in an abrupt, sustained decrease in heart rate indicating that the increase in heart rate associated with tethering was due to persistent stimulation of the sympathetic nervous system. Since multiple aspects of cardiovascular function are influenced by the sympathetic nervous system, and other organs and systems (e.g., pituitary-gonadal) also may be affected, investigators using the swivel-tether system should be cognizant of these potential effects when designing experiments and interpreting the results.     

Formation and turnover of long-chain fatty acid esters of 5-androstene-3 beta, 17 beta -diol in estrogen receptor positive and negative human mammary cancer cell lines in culture

Microsomal preparations derived from bovine placenta cotyledons, previously investigated as a convenient source of fatty acyl coenzyme A: estradiol-17 beta-acyl transferase, have been shown to acylate other steroids bearing 3 beta- or 17 beta-hydroxyl groups. In the presence of 0.1 mM oleoyl CoA, the apparent Km values for dehydroepiandrosterone, testosterone, and 5-androstene-3 beta,17 beta-diol (delta 5-DIOL) were 45, 67, and 20 microM, respectively. Acylation of delta 5-DIOL occurred at either the 3 beta- or 17 beta-positions to give monoesters. Testosterone, estradiol-17 beta, and delta 5-DIOL acted as competitive inhibitors for the acylation of the 3 beta-hydroxyl group of dehydroepiandrosterone (Ki values 71, 75, and 41 microM, respectively). Such data indicate that a single enzyme of wide substrate specificity may be involved in these acylation reactions. When estrogen receptor (ER) positive and negative human mammary cancer cell lines were incubated with 10 nM [3H]delta 5-DIOL, intracellular accumulation of delta 5-DIOL long-chain fatty acid esters occurred; rates being higher (p less than 0.001) in ER negative cells (MDA-MB-231 and MDA-MB-330) compared to MCF-7 cells (ER positive), and higher (P less than 0.005) in MDA-MB-231 cells compared to ZR-75-1 cells (ER positive). After exposure to 10 nM [3H]delta 5-DIOL for 16 h, the total labeled steroid fatty acid fraction was composed predominantly of delta 5-DIOL-3 beta- and 17 beta-monoesters (approximately 85%), the remainder containing approximately equal amounts of delta 5-DIOL-diesters and dehydroepiandrosterone-3 beta-esters. Subsequent transfer to medium lacking delta 5-DIOL was accompanied by a breakdown of the labeled esters, which was more rapid in the ER positive cell lines. During this period, intracellular free delta 5-DIOL levels rapidly declined in MDA-MB-330 cells but were maintained in MCF-7 cells, presumably by binding to ER. This behavior parallels that of estradiol-17 beta previously observed in these cell lines and further emphasizes the potential importance of the adrenal-derived estrogen delta 5-DIOL in consideration of a hormone-based etiology of human breast cancer.     

DIDS decreases CSF HCO3- and increases breathing in response to CO2 in awake rabbits

An inhibitor of the HCO3-/Cl- exchange carrier protein, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) or vehicle was infused in mock cerebrospinal fluid (CSF) via the cisterna magna in conscious rabbits at 10 mumol/l for 40 min at 10 microliter/min. Neither treatment had any effect over 2-5 h on the non-CO2-stimulated CSF ion values or blood gases. With CO2 stimulation such that arterial PCO2 (PaCO2) was increased 25 Torr over 3 h, DIDS treatment significantly decreased the stoichiometrically opposite changes in CSF [HCO3-] and [Cl-] that normally accompany hypercapnia and reflect ionic mechanisms of CSF pH regulation. Expressed as delta CSF [HCO3-]/delta PaCO2, DIDS treatment decreased the CSF ionic response by 35%. In a separate paired study design DIDS administration via the same protocol had no effect on resting ventilation but significantly increased the ventilation and tidal volume responses to a 28-Torr increase in PaCO2. Expressed as change in minute ventilation divided by delta PaCO2, DIDS treatment produced a 39.6% increase. The results support the concept of a DIDS-inhibitable anion exchange carrier being involved in CSF pH regulation in hypercapnia and suggest a DIDS-related effect on the ventilatory response to CO2.     

Understorey vegetation change in a Picea mariana chronosequence

Eighteen black spruce (Picea mariana) stands, representing postfire ages of 26 to 120 yr, were surveyed for understorey vegetation and site/microsite characteristics at two spatial scales. This enabled comparison of within- versus among-stand compositional variation.Detrended correspondence analysis (DCA) ordination among the 18 stands revealed a complex age/moisture gradient. DCA ordination among 1 800 quadrats within the stands indicated a similar gradient with much compositional overlap. Quadrats were grouped, using two-way indicator species analysis (TWINSPAN), into 9 classes each representing a phase in understorey vegetation composition. These phases shifted in abundance from young to old stands with a high degree of concordance among replicates in the same age class. Understorey succession is strongly linked to the stages in tree growth, mortality and thinning coupled with the accumulation of site moisture.Abbreviations DCA Detrended Corrospondence Analysis