Evaluation of methodological and biological influences on the collection and composition of exhaled breath condensate

The purpose of this inter-species comparison (calves and pigs) was to identify methodological and biological influences on the collection and composition of exhaled breath condensate (EBC). A total of 352 EBC samples were collected, whilst variables of ventilation were registered in parallel. Partial pressure of carbon dioxide (pCO₂) and pH were analysed in non-degassed EBC samples. The concentration of total protein in EBC was measured colorimetrically. In both species, lung function was evaluated before and after EBC collection. Statistical analyses were performed to study the effect of EBC collection on lung function and to identify the influence of ventilatory variables on the collection and composition of EBC. Collection of EBC did not affect lung function. Despite the volume of EBC collected per unit time being primarily dependent on ventilation per unit time, species-specific conditions during the EBC collection process resulted in different dependences of EBC collection from other variables of ventilation (i.e. maximal airflow during expiration or expired tidal volume kg^-1 body weight). The concentration of protein ml^-1 EBC increased with the expired volume per min and with peak expiratory flow. Although the pCO₂ in fresh EBC was significantly negatively dependent on the duration of collection, comparable pHs (5.6 - 6.2) were measured in EBC of both calves and pigs. The obtained data may help one standardize EBC collection in different species.     

Comparative population genetics of seven notothenioid fish species reveals high levels of gene flow along ocean currents in the southern Scotia Arc, Antarctica

The Antarctic fish fauna is characterized by high endemism and low species diversity with one perciform suborder, the Notothenioidei, dominating the whole species assemblage on the shelves and slopes. Notothenioids diversified in situ through adaptive radiation and show a variety of life history strategies as adults ranging from benthic to pelagic modes. Their larval development is unusually long, lasting from a few months to more than a year, and generally includes a pelagic larval stage. Therefore, the advection of eggs and larvae with ocean currents is a key factor modulating population connectivity. Here, we compare the genetic population structures and gene flow of seven ecologically distinct notothenioid species of the southern Scotia Arc based on nuclear microsatellites and mitochondrial DNA sequences (D-loop/cytochrome b). The seven species belong to the families Nototheniidae (Gobionotothen gibberifrons, Lepidonotothen squamifrons, Trematomus eulepidotus, T. newnesi) and Channichthyidae (Chaenocephalus aceratus, Champsocephalus gunnari, Chionodraco rastrospinosus). Our results show low-population differentiation and high gene flow for all investigated species independent of their adult life history strategies. In addition, gene flow is primarily in congruence with the prevailing ocean current system, highlighting the role of larval dispersal in population structuring of notothenioids.     

Head-bobbing of walking birds

Many birds show a rhythmic forward and backward movement of their heads when they walk on the ground. This so-called “head-bobbing” is characterized by a rapid forward movement (thrust phase) which is followed by a phase where the head keeps its position with regard to the environment but moves backward with regard to the body (hold phase). These head movements are synchronized with the leg movements. The functional interpretations of head-bobbing are reviewed. Furthermore, it is discussed why some birds do bob their head and others do not.     

Binding site specificity of gamma-radiation-induced crosslinking between phenylalanine and a phenylalanine-containing tetrapeptide

The binding site specificity of crosslinking mediated by the hydroxyl radical has been investigated in a simple model system: a tetrapeptide, Gly-Gly-Phe-Leu, and 14C-labeled phenylalanine. Crosslinking leads to the tetrapeptide-phenylalanine adduct which has been isolated by gel filtration. The amino acid analysis of these adducts compared with those of gamma-radiation-induced dimers of the tetrapeptide and of the dipeptide, Gly-Phe, shows that only the phenylalanine residue is affected and that the same new peaks appear in each case. Spectrophotometric measurement indicates that the extinction coefficient at 260 nm of dimeric tetrapeptide is four times higher than that of monomeric, as is dimeric phenylalanine compared to monomeric. These observations suggest a common crosslinking mechanism in all three cases that involves the aromatic ring of phenylalanine. The appearance of several radioactive peaks in the gel filtration separation of the acid hydrolysate of the adduct suggests that the crosslinking involves more than one possible modification of the phenylalanine. Three distinct tetrapeptide-Phe species, corresponding to molecular weights of 555, 573, and 591, were observed by fast atom bombardment mass spectrometry. The partial release of radioactive phenylalanine from the tetrapeptide-phenylalanine adducts by acid hydrolysis indicates the liability of some phenylalanine-phenylalanine bonds.     

Atretogenic action of estrogen in rhesus monkeys: Effects of repeated treatment

The effects of 17β-estradiol (E₂), administered in Silastic capsules for 24 hours at intervals of 10 or 14 days, on follicular development and menstrual cycle characteristics were studied in 13 rhesus monkeys. In seven monkeys receiving E₂ at l0-day intervals for 50 treatment periods, new follicles frequently developed between treatments but usually regressed. In seven instances, the follicles persisted longer than expected but were steroidogenically suppressed and regressed spontaneously. Ovulation occurred in only two instances. In six monkeys receiving E₂ at 14-day intervals, new follicles developed regularly, with seven ovulations occurring in 37 treatment periods. A persistent anovulatory follicle was noted in only one instance. Menstruation occurred with equal frequency, and the interval from treatment to onset of menstruation was not significantly different regardless of treatment or the occurrence of ovulation; the intervals between menstruation approximated those of normal menstrual cycles. In general, following termination of treatment, menstrual cycles returned to normal quickly. These data indicate that E₂ administered intermittently at 10-day intervals effectively suppresses ovulation, and they provide new insight into the actions of E₂ on folliculogenesis in primates.     

Increased levels of dihydrofolate reductase mRNA can be measured in normal, growth-stimulated mouse fibroblasts

Levels of mRNA for the enzyme dihydrofolate reductase (EC 1.5.1.3) were determined in growth-stimulated 3T6 cells which contained wild-type dosage of the gene coding for this enzyme. As in the case of methotrexate-resistent cells having highly amplified levels of genes for dihydrofolate reductase, an increase in dihydrofolate reductase mRNA by a factor of 2–4 can be determined when cells enter the S phase. This increase is inhibited by sodium butyrate (which inhibits growth-stimulated 3T6 cells in mid G1 phase) but not by hydroxyurea (which inhibits in early S phase). We conclude that with the available methods it is possible to study the regulation of S phase-specific enzymes after growth stimulation at the level of the mRNA, even if gene amplification is not possible or desirable.