Vertical bars on male Xiphophorus multilineatus: a signal that deters rival males and attracts females

We examined the function of the vertical bar pattern on maleswordtails (Xiphophorus multilinneatus) as a signal in bothmale-male competition and female choice. This pattern had previouslybeen described as an aggressive signal because males intensifiedthe bars during male-male encounters in the laboratory. Ourfield observations supported this observation and also showedthat bars intensified when males courted females. The intensityof bars was correlated with access to females in the field.Within the size range of males that have bars, however, neitherbar number nor male size appeared to influence access to females.We used freeze-branding to remove the bars from males in thelaboratory so that we could control for characters correlatedwith bar intensity, and tested males and females separatelyso that we could separate the influence of these two componentsof sexual selection. We compared the responses of males andfemales to males that had their bars removed and control malesfreeze-branded between the bars. Test males responded more aggressivelyto males without bars as compared to control males. In addition,females showed a preference for control males over males thathad their bars removed. These results suggest that the barsmay function as a signal that deters rival males and attractsfemales.     

Foot-and-mouth disease virus 2A oligopeptide mediated cleavage of an artificial polyprotein.

We describe the construction of a plasmid (pCAT2AGUS) encoding a polyprotein in which a 19 amino acid sequence spanning the 2A region of the foot-and-mouth disease virus (FMDV) polyprotein was inserted between the reporter genes chloramphenicol acetyl transferase (CAT) and beta-glucuronidase (GUS) maintaining a single, long open reading frame. Analysis of translation reactions programmed by this construct showed that the inserted FMDV sequence functioned in a manner similar to that observed in FMDV polyprotein processing: the CAT2AGUS polyprotein underwent a cotranslational, apparently autoproteolytic, cleavage yielding CAT-2A and GUS. Analysis of translation products derived from a series of constructs in which sequences were progressively deleted from the N-terminal region of the FMDV 2A insertion showed that cleavage required a minimum of 13 residues. The FMDV 2A sequence therefore provides the opportunity to engineer either whole proteins or domains such that they are cleaved apart cotranslationally with high efficiency.     

Polymorphism analysis of the prion gene in BSE-affected and unaffected cattle

Polymerase chain reaction (PCR) primers designed to amplify the octapeptide repeat region of the bovine prion gene were used to test the association of genotypes with bovine spongiform encephalitis (BSE) in 56 BSE-affected and 177 unaffected animals. Three alleles (A, B, C) were detected as single-strand conformation polymorphisms (SSCPs) and two alleles (1,2 representing six or five copies of the octapeptide repeat respectively) were detected as amplified double-strand fragment length polymorphisms (AMFLPs). Observed genotypes of SSCPs and AMFLPs were analysed by x-square. The SSCP genotypes of nuclear family members of animals with BSE and BSE-affected animals were different (P < 0.001, P < 0.01) from unrelated animals of the same breed without BSE. No genotypic differences were found between the BSE-affected animals and their relatives (P > 0.469). No AMFLP genotypic differences were detected between BSE-affected animals, their relatives, unrelated animals of the same breed or animals of different breeds (P > 0.05). These data suggest that BSE-affected animals and their relatives are more likely to have the AA SSCP genotype than unrelated animals of the same breed or animals of different breeds.     

Vascular Development and Sap Flow in Apple Pedicels

Xylem and phloem tissues of the pedicel of apple fruit increasein cross-sectional area throughout development. The increasein phloem is similar in the two cultivars examined (Cox's OrangePippin and Royal Gala) and reflects a steadily increasing phloemsap flow to the fruit. The increase in xylem tissue is due toa proliferation of non-conducting, structural, components sinceclose examination reveals no increase in the number of vesselelements from just after flowering onwards. The greater number,and the larger diameter, of the vessels in Cox's explains theinitially higher xylem conductance found in this cultivar. In vitro measurements of xylem exudation reveal a decline duringthe growing season in the xylem conductance of both cultivarsand an increasing proportion of fruit (particularly in Cox's)in which the xylem comes to be totally non-conducting. Thisobservation is in line with previously reported measurementsof xylem sap flow in vivo. The straightforward techniques used in this study offer a feasiblealternative to more arduous methods of assessing xylem and phloemsap flows and their balance during growth.Copyright 1994, 1999Academic Press Apple, xylem, phloem, vascular development, sap flow, Malus domestica Borkh     

Follicular development during early pregnancy and the estrous cycle of the sow

The objective of this study was to monitor and compare follicle populations and follicular development in pregnant and nonpregnant sows from Day 3 to Day 20 after breeding. Twenty-four sows were paired within parity on the day of artificial insemination and were randomly allocated within pair for insemination with either killed (n=12) or live spermatozoa (n=12). All the sows were artificially inseminated with the pooled ejaculate of the same boar. From Day 3 through Day 20 post estrus, ovarian follicles were scanned daily by ultrasonography. Ultrasound images were recorded on videotape and were retrospectively analyzed. Follicles were mapped to indentify the existence of follicular waves. The follicles were then classified as small (< 3 mm), medium (3-5 mm), or large (>/=5 mm). Pregnancy diagnosis was performed on Day 21 by ultrasonography. Pregnant sows maintained a constant proportion of the follicle population in the small, medium and large follicle categories. However, in the nonpregnant sows, the proportion of follicles in the various size categories remained constant until Day 15. Thereafter, the proportion of small follicles decreased (P < 0.05) from Day 15 to 20, and the proportions of medium and large follicles increased (P < 0.05). The predictability of pregnancy status on Day 20 based on follicle populations in any of the 3 follicle categories was low. Moreover, there was no evidence of follicular waves during the estrous cycle or early pregnancy. In conclusion, the proportion of small follicles decreased while medium and large follicle increased from Day 15 through Day 20 of the estrous cycle, but not during a similar stage of pregnancy. This latter finding concurs with follicle recruitment from the pool of small follicles for ovulation following PGF2alpha secretion to induce luteolysis, which reduces progesterone concentrations and thereby allows for the stimulation of the pool of small follicles by gonadotropins.     

Induction of feline immunodeficiency virus-specific cytotoxic T cells in vivo with carrier-free synthetic peptide.

The role of cellular immunity in the establishment and progression of immunosuppressive lentivirus infection remains equivocal. To develop a model system with which these aspects of the host immune response can be studied experimentally, we examined the response of cats to a hybrid peptide containing predicted T-and B-cell epitopes from the gag and env genes of feline immunodeficiency virus (FIV). Cats were immunized with an unmodified 17-residue peptide incorporating residues 196 to 208 (from gag capsid protein p24) and 395 to 398 (from env glycoprotein gp120) of the FIV Glasgow-8 strain by using Quil A as an adjuvant. Virus-specific lymphocytotoxicity was measured by chromium-51 release assays. The target cells were autologous or allogeneic skin fibroblasts either infected with recombinant FIV gag vaccinia virus or pulsed with FIV peptides. Effector cells were either fresh peripheral blood mononuclear cells or T-cell lines stimulated with FIV peptides in vitro. Cytotoxic effector cells from immunized cats lysed autologous, but not allogeneic, target cells when they were either infected with recombinant FIV gag vaccinia virus or pulsed with synthetic peptides comprising residues 196 to 205 or 200 to 208 plus 395. Depletion of CD8+ T cells, from the effector cell population abrogated the lymphocytotoxicity. Immunized cats developed an antibody response to the 17-residue peptide immunogen and to recombinant p24. However, no antibodies which recognized smaller constituent peptides could be detected. This response correlated with peptide-induced T-cell proliferation in vitro. This study demonstrates that cytotoxic T lymphocytes specific for FIV can be induced following immunization with an unmodified short synthetic peptide and defines a system in which the protective or pathological role of such responses can be examined.     

Woody-tissue respiration for Simarouba amara and Minquartia guianensis,two tropical wet forest trees with different growth habits

We measured CO₂ efflux from stems of two tropical wet forest trees, both found in the canopy, but with very different growth habits. The species were Simarouba amara, a fast-growing species associated with gaps in old-growth forest and abundant in secondary forest, and Minquartia guianensis, a slow-growing species tolerant of low-light conditions in old-growth forest. Per unit of bole surface, CO₂ efflux averaged 1.24 mol m^–2 s^–1 for Simarouba and 0.83 mol m^–2s^–1 for Minquartia. CO₂ efflux was highly correlated with annual wood production (r ²=0.65), but only weakly correlated with stem diameter (r ²=0.22). We also partitioned the CO₂ efflux into the functional components of construction and maintenance respiration. Construction respiration was estimated from annual stem dry matter production and maintenance respiration by subtracting construction respiration from the instantaneous CO₂ flux. Estimated maintenance respiration was linearly related to sapwood volume (39.6 mol m^–3s^–1 at 24.6° C, r ²=0.58), with no difference in the rate for the two species. Maintenance respiration per unit of sapwood volume for these tropical wet forest trees was roughly twice that of temperate conifers. A model combining construction and maintenance respiration estimated CO₂ very well for these species (r ²=0.85). For our sample, maintenance respiration was 54% of the total CO₂ efflux for Simarouba and 82% for Minquartia. For our sample, sapwood volume averaged 23% of stem volume when weighted by tree size, or 40% with no size weighting. Using these fractions, and a published estimate of aboveground dry-matter production, we estimate the annual cost of woody tissue respiration for primary forest at La Selva to be 220 or 350 g C m^–2 year^–1, depending on the assumed sapwood volume. These costs are estimated to be less than 13% of the gross production for the forest.     

Purification of Potato Leaf Plasma Membrane Protein pp34, a Protein Phosphorylated in Response to Oligogalacturonide Signals for Defense and Development

A potato (Solanum tuberosum L.) plasma membrane protein called pp34, the only known example of a plasma membrane protein that is phosphorylated specifically in response to defined Oligogalacturonide signals in plants, has been purified to apparent homogeneity. Polyclonal antibodies raised in rabbits against the purified pp34 protein immunoprecipitated a single thiophosphorylated protein species from potato plasma membranes, as analyzed by two-dimensional denaturing electrophoresis and fluorography. The pp34 antibodies also recognized a single protein in tomato (Lycopersicon esculentum L.) membranes that is thiophosphorylated in response to Oligogalacturonide elicitors, as demonstrated by western blotting and specific immunoprecipitation. These experiments confirm the identity of the tomato membrane protein as a pp34 homolog and establish the high monospecificity of the pp34 antibodies. This will permit further investigation of the role of protein phosphorylation in oligouronide signaling for defensive genes in potato and tomato plants.