Mediators of the biphasic responses of bone to intermittent and continuously administered parathyroid hormone

Parathyroid hormone (PTH) has biphasic effects on bone: continuous treatment is catabolic whereas intermittent treatment is anabolic. The mechanism(s) responsible for these differing effects are still unclear, partly because of the previous non-availability of a model system in which effects on both formation and resorption indices could be studied concomitantly. In cultured marrow cells from 6-week old C57BL/6 mice, we demonstrated that 4 days of intermittent PTH treatment increased mRNA for osteoblast differentiation markers (Runx2, alkaline phosphatase (AP), and type I procollagen (COL1A1) whereas continuous treatment resulted in production of large numbers of TRAP-positive multinucleated osteoclasts. Although IGF-I mRNA did not increase after intermittent treatment, it was consistently higher than after continuous treatment, and the addition of an anti-IGF-I neutralizing antibody prevented the increase in bone formation indices observed with intermittent treatment. By contrast, after continuous treatment, gene expression of RANK ligand (RANKL) was increased and that of osteoprotegerin (OPG) was decreased, resulting in a 25-fold increase in the RANKL/OPG ratio. In this model system, the data suggest that intermittent PTH treatment enhances osteoblast differentiation through an IGF-I dependent mechanism and continuous PTH treatment enhances osteoclastogenesis through reciprocal increases in RANKL and decreases in OPG.     

Female preference for large males in sailfin mollies,<Emphasis Type="Italic"> Poecilia latipinna</Emphasis>: the importance of predation pressure and reproductive status

We examined the effect of predation risk on female association patterns in the live-bearing sailfin molly (Poecilia latipinna). We tested two classes of females, with and without the risk of predation by a green sunfish (Lepomis cyanellus): (1) postpartum females (maintained with males until visibly gravid, then isolated and tested within 24–48 h of dropping a brood); and (2) non-postpartum females (different females, isolated from males for >50 days). When there was no apparent risk of predation, postpartum females showed a significant preference for large over small males, whereas non-postpartum females showed no size preference at all. When there was an apparent risk of predation, postpartum females maintained their preference for larger males and non-postpartum females continued to show no preference for large or small males. These results suggest that reproductive status (receptivity) plays a greater role in mate preference than predation risk. For postpartum females, the cost of not choosing a preferred mate may outweigh the potential cost of predation. Non-postpartum females either do not benefit from mating or are being indecisive about mating and thus are less likely to be choosy whether or not a predator is present.Communicated by I. Schlupp     

Biofilm-specific cross-species induction of antimicrobial compounds in bacilli

An air-membrane surface (AMS) bioreactor was designed to allow bacteria to grow attached to a surface as a biofilm in contact with air. When Bacillus licheniformis strain EI-34-6, isolated from the surface of a marine alga, was grown in this reactor, cells produced antimicrobial compounds which they did not produce when they were grown in shake flask cultures. An unidentified red pigment was also produced by surface-grown cells but not by planktonically grown cells. Glycerol and ferric iron were important for the production of antimicrobial compounds and the red pigment. Release of these secondary metabolites was not due to the onset of sporulation. Cell-free spent medium recovered from beneath the reactor membrane could induce production of antimicrobial compounds and red pigment in shake flask cultures. Neither glycerol nor ferric iron was required for production of these inducer compounds. Spent medium from beneath the membrane of an AMS bioreactor culture of Bacillus subtilis strain DSM10(T) and Bacillus pumilus strain EI-25-8 could also induce production of antimicrobial compounds and a red pigment in B. licheniformis isolate EI-34-6 grown in shake flask cultures; however, the corresponding spent medium from shake flask cultures of DSM10(T) and EI-25-8 could not. These results suggest that there is a biofilm-specific cross-species signaling system which can induce planktonically grown cells to behave as if they were in a biofilm by regulating the expression of pigments and antimicrobial compounds.     

Skin graft survival in genetically identical cloned pigs

Nuclear transfer technology allows for the reprogramming of somatic cells, and the production of embryonic stem cells and animals that are genetically identical in terms of nuclear DNA to the parental somatic cell. It is assumed that these products of nuclear transfer technology will be immunologically compatible to each other in spite of the fact that there are data that show differences in the expression patterns and phenotypes between animals produced by nuclear transfer. We have produced a series of cloned pigs from embryonic fibroblasts. Microsatellite analysis was used to confirm that the clones were genetically identical. Skin transplants were performed to assess immunological reactivity. Skin transplants between genetically identical cloned pigs were accepted, whereas third party grafts were rejected. Histological analysis of the grafts showed edema and mononuclear cell infiltrates in the recipient's skin in rejected grafts and not in grafts that were accepted. Our data supports the notion that genetically identical cloned pigs are immunologically compatible.     

Renal C-type natriuretic peptide and natriuretic peptide receptor B mRNA expression are affected by water deprivation in the Spinifex Hopping mouse

This study investigated the effect of water deprivation on the expression of C-type natriuretic peptide (CNP) and natriuretic peptide receptor B (NPR-B) mRNA, and the ability of NPR-B to generate cGMP in the Spinifex Hopping mouse, Notomys alexis. This rodent is a native of central and western Australia that is well adapted to survive in arid environments. Initially, CNP and NPR-B cDNAs (partial for NPR-B) were cloned and sequenced, and were shown to have high homology with those of rat and mouse. RT-PCR analysis showed CNP mRNA expression in the kidney, proximal and distal colon and small intestine, whilst NPR-B mRNA expression was found in the kidney, proximal and distal colon and the atria. Using a semi-quantitative multiplex PCR technique, the expression of renal CNP and NPR-B mRNA was determined in 7- and 14-day water-deprived hopping mice, in parallel with control hopping mice (access to water). Water deprivation significantly decreased the relative levels of CNP and NPR-B mRNA expression in both the 7- and 14-day water-deprived hopping mice, when compared to control hopping mice. In contrast, the ability of CNP to stimulate cGMP production was significantly increased after 14 days of water deprivation. This study shows that alterations in the renal CNP/NPR-B system may be an important physiological adjustment when water is scarce.     

Time of day and water temperature modify the physiological stress response in green sturgeon,Acipenser medirostris

The effects of time of day and water temperature on the acute physiological stress response were investigated in young-of-the-year green sturgeon (Acipenser medirostris). The response to a 1-min air-emersion stressor was assessed during the day (08.00 h) and at night (20.00 h), as well as after acclimation to either 11 degrees C or 19 degrees C. Blood samples were collected prior to stress and at several times after exposure to the stressor, and plasma concentrations of cortisol, lactate, and glucose were determined. The magnitudes of cortisol (19.1 ng ml(-1) vs. 4.9 ng ml(-1)) and lactate (190.6 mg l(-1) vs. 166.7 mg l(-1)) were significantly higher in fish stressed at night when compared with the day. There were no significant differences in glucose levels between time periods. Although, acclimation temperature did not affect peak cortisol concentrations (56.7 and 50.3 ng ml(-1) at 11 degrees C and 19 degrees C, respectively), the duration of the response was significantly extended at 11 degrees C. Post-stressor lactate increases were similar between temperature groups, but at 11 degrees C post-stressor glucose levels were significantly increased through 6 h, suggesting stressor-induced glycogenolysis and gluconeogenesis or decreased glucose utilization. These data demonstrate that the physiological stress response in green sturgeon is modified by both time of day and temperature.     

Husbandry, handling, and nutrition for marmosets

Marmosets, especially Callithrix jacchus, have become an established part of the laboratory animal community. Information on marmoset life history, behavior, and diet acquired from experience with natural and captive habitats has increased, but the early information from workers with colonies, principally those of tamarins, has led to some common perceptions about how to house, handle, and especially, feed callitrichids that may not apply to marmoset requirements. The availability of commercially produced, almost-complete base diet components and a wider variety of cage construction materials, combined with the recent emphasis on the integration of engineering and performance standards for housing, have made captive life and the implementation of research requirements better for the animals and the people that work with them. We will review some of the routine aspects of husbandry, handling, and nutrition for marmoset monkeys maintained in a research setting.     

Purification of Piscirickettsia salmonis and associated phage particles

Piscirickettsia salmonis was isolated from cell culture using differential centrifugation and purified on a 30% Percol gradient. The purity of the preparation was assessed by transmission electron microscopy and phage-like particles were found to be associated with some of the P. salmonis isolates examined. This is believed to be the first report of a phage associated with rickettsia from fish.     

Observations on the electron-dense bodies of the PKX parasite, agent of proliferative kidney disease in salmonids

Ultrastructural observations on structures associated with the 'haplosporosome'-like electron-dense bodies (EDBs) of the primary cell of the extrasporogonic stage of PKX are described. Observations made include formation of EDBs by the trans-Golgi network, an additional membrane associated with EDB structure, confronting cisternae, engulfment and presence of EDBs in multivesicular bodies, fusion of EDBs with the plasmalemma, degeneration of EDBs in disintegrating primary cells and endocytosis of PKX cytoplasm by adherent macrophages. Immunogold localisation of a PKX-specific monoclonal antibody (MAb A3) suggests that the EDBs contain periodate-sensitive carbohydrates on their membranes. Tissues prepared for immunogold electron microscopy further suggest that some contain a lipid-rich core. An interpretation is made on their possible function and their relationship with the haplosporosomes and sporoplasmasomes found in members of the Haplosporidea and Myxosporea respectively.     

Functional and evolutionary consequences of pyrethroid resistance mutations in S6 transmembrane segments of a voltage-gated sodium channel

Pyrethroids are a class of voltage-dependent sodium channel modifiers widely used as insecticides for control of disease vectors and agricultural pests. Many insect populations have developed resistance to pyrethroids linked to nervous system insensitivity and structural mutations in neuronal sodium channels. Pyrethroid resistant strains of the moth Heliothis virescens carry single point mutations leading to amino acid substitutions in either transmembrane segment I-S6 (V421M) or II-S6 (L1029H) of the para-homologous sodium channel. We analyzed the consequences of V421M and L1029H mutations constructed in the Drosophila para sodium channel heterologously expressed in Xenopus oocytes, and found that both mutations confer channel insensitivity to permethrin, with the L1029H mutation having a more pronounced effect. Both mutations also modify the intrinsic voltage-dependent gating properties of the channel, but L1029H less so than V421M. These results suggest that mutation V421M exacts a higher fitness cost than L1029H, providing a plausible explanation for genetic succession observed in field strains, where V421M was replaced by L1029H during the past decade.