Evidence that de novo protein synthesis participates in a time-dependent augmentation of the chemotactic peptide-induced respiratory burst in neutrophils: Effects of recombinant human colony stimulating factors and dihydrocytochalasin B

We examined the effects of the recombinant human colony stimulating factors GM-CSF and G-CSF, cycloheximide (a protein synthesis inhibitor) and dihydrocytochalasin B (a microfilament disrupting agent) upon FMLP (N-formyl-methionyl-leucylphenylalanine)-stimulated O₂ ⁻ production by neutrophils. We confirmed a time dependent augmentation of O₂ ⁻ production following preincubation of neutrophils either alone or with colony stimulating factors. Furthermore, we found that GM-CSF, but not G-CSF, increased O₂ ⁻ production at some concentrations of the stimulus. Preincubation of neutrophils with cycloheximide in the absence of CSF caused a marked fall in O₂⁻-production that was first evident at 2 hours. The fall in O₂⁻-forming capacity caused by cycloheximide was much less pronounced if dihydrocytochalasin B was also included in the preincubation buffer. These findings suggest a previously unrecognized role for de novo protein synthesis in maintaining the ability of neutrophils to manufacture O₂⁻, and support earlier studies indicating that the cycling of FMLP receptors between the cell membrane and an intracellular compartment is important in determining the magnitude of the respiratory burst in FMLP-stimulated neutrophils.     

Interaction of opioid peptides and other drugs with multiple delta ncx binding sites in rat brain: further evidence for heterogeneity.

Recent pharmacological data strongly support the hypothesis of δ receptor subtypes as mediators of both supraspinal and spinal antinociception (δ₁ and δ₂ receptors). In vitro ligand binding data, which are fully supportive of the in vivo data, are still lacking. A previous study indicated that [³H][ -Ala², -Leu⁵]enkephalin labels two binding sites in membranes depleted of μ binding sites by pretreatment with the site-directed acylating agent, 2-(p-ethoxybenzyl)-1-diethylaminoethyl-5-isothiocyanatobenzimidazole-HCI (BIT). The main goal of the present study was to develop a ligand-selectivity profile of the two δ_ncx binding sites. The data indicated that naltrindole and oxymorphindole were relatively selective for site 1 (20-fold). [ -Ser²,Thr⁶]Enkephalin and deltorphin-II were only 2.7-fold and 2.2-fold selective for site 1. [ -Pen², -Pen⁵]Enkephalin and deltorphin-I were 80-fold and 38-fold selective for site 2.3-Iodo-Tyr- -Ala-Gly-Phe- -Leu was 52-fold selective for site 1. Morphine had moderate affinity for site 1 (K_i = 16 nM), and was about 11-fold selective for site 1. Thus, of the 10 drugs studied, only DPDPE and DELT-I were selective for site 2. Viewed collectively with other data, it is likely that the δ₁ receptor and the δ_ncx binding site are synonymous.     

Cooperative enhancement of reproductive success in white-winged choughs

Summary White-winged choughs are a cooperatively breeding species which provide parental care to their young over an entire year. I traced the reproductive success of groups of white-winged choughs from the start of one breeding season to the next over 3 years. I examined the effect of helper number on timing of breeding, the success of each effort, the number of efforts made in a season, and the final reproductive success at the end of each year. Timing of commencement of breeding varied between years but was not related to group size. Early broods were not more successful than late broods. Nest building (July–September) commenced earlier in years which had high rainfall in July; choughs rely on rainfall for supplies of mud for nest construction. Most nest failures occurred gradually and were attributed to starvation of nestlings, although some sudden failures were attributed to predation. Large groups have more young by the beginning of the following season; this is due to higher fledging success and a greater likelihood of having second broods. Disappearance of young after fledging and during the transition to independence was not dependent on group size. Only groups of seven and above produce more than one young on average over the entire year; choughs provide one of the most marked cases for helpers enhancing the reproductive success of breeders. Large groups are virtually guaranteed of reproductive success over the whole year and grow more quickly than small groups. These results highlight the need to consider the effect of helpers over the entire period of reproduction and care of young, rather than just at fledging.     

Brood raiding and the population dynamics of founding and incipient colonies of the fire ant, Solenopsis invicta

Abstract. 1. One of the first activities of minim workers in incipient fire ant nests is mutual brood raiding, the amalgamation of nests through the reciprocal stealing of brood and defection of workers.
2. Discrete mating flights created cohorts of incipient colonies. About 25% of founding nests survived the claustral period of 16–48 days (depending on season). Early incipient colony mortality was 5–6% per day. Over 60% of this mortality was accounted for through brood raiding. Most colonies raided when each cohort first became active, and many raided more than once. Raid size (number of nests, duration, distance) tended to increase during the summer as colonies grew through raiding. After the raiding period, nest mortality rate dropped 3–10-fold. Only 1–3% of founding nests were still alive at this time.
3. Queens from losing or failed nests tended to abandon their nests and attempted to enter successful ones, often following raiding trails to do so. This emigration was at least as successful as non-emigration in ultimately achieving the status of reproductrix of a successful nest (about 4%).
4. Brood raiding is a dominant process in early population dynamics, probably accounting for most of the early nest mortality. Its effect is to change the venue and unit of competition from nest-against-nest to a shifting aggregation of queens, workers and brood involving entire local populations. Nest thinning is thus very rapid, and the boost to the size of winning nests very large, allowing raiding colonies to win the competition for territory, and to achieve the early colony maturity so important to this, and other, weedy species. The importance of winning brood raids may also have driven increased minim production through the evolution of pleometrosis.     

Monogamy to communal breeding: exploitation of a broad resource base by burying beetles (Nicrophorus)

Abstract.

• 1 To investigate the range of resource size that burying beetles (Nicrophorus) exploit, small (21–33 g), medium (50–90 g) and large (120–210g) carcasses, were placed in the field and then exhumed after 1, 4, 8, 12 or 18 days.
• 2 Nicrophorus attempts to utilize carcasses over this entire size range but has greater success on smaller carcasses.
• 3 Larger carcasses were more difficult to exploit because: (a) they took longer to conceal beneath the leaf litter; (b) they were less likely to be rounded into brood balls; (c) they were more likely to be utilized by dipterans; and (d) they were occupied by greater numbers of congeners.
• 4 Larger carcasses, however, did support greater numbers of larvae and contained broods of greater total mass than smaller carcasses.
• 5 Beetles sometimes bred communally on larger carcasses in the field and same-sex adults were observed to feed young.
• 6 Two follow-up experiments were conducted in the laboratory. On a large carcass N.defodiens, N.tomentosus or N.orbicollis can raise a maximum of 35–50 young. Nicrophorus pustulatus, in contrast, appears to be unique among Nicrophorus in that it can raise nearly 200 young on larger carcasses.
• 7 Nicrophorus orbicollis and Nicrophorus sayi are extremely dependent on parental regurgitations and young fail to survive to the second instar if parents are removed. Young of Nicrophorus defodiens, N.tomentosus and N.pustulatus can develop normally without parental regurgitations.
• 8 I discuss these results in the context of reproduction on carcasses of different size and hypothesize that this breeding system is facultatively quasisocial.

     

Characteristics of small cell colonies developing in primary cultures of adult rat hepatocytes

Phenotypes of the cells developing into small colonies after days of primary culture of adult rat hepatocytes in serum-free modified Dulbecco Modified Eagles’ medium containing 10 mM nicotinamide and 10 ng/ml epidermal growth factor were analyzed immunocytochemically, cytochemically and ultrastructurally. Albumin, cytokeratin 8 and 18 were seen by immunocytochemical techniques in the cells of the small colonies at Day 6. Transferrin, α-antitrypsin, ceruloplasmin, and haptoglobin, proteins secreted by mature hepatocytes, were faintly stained in these cells as was α-fetoprotein. These proteins were secreted into the culture medium as evidenced by immunoblot analysis. γ-Glutamyltransferase, alkaline phosphatase and glucose 6-phosphatase were not present in the cells of the small colonies as well as the surrounding hepatocytes at Day 6 of culture. In addition, ultrastructural examinations of the cells in the small colonies indicated that these cells not only had many characteristic mitochondria and desmosomes, but also a few small peroxisomes. Such cells, even after 20 days in culture were proliferating, as evidenced by the intranuclear presence of the proliferating cell nuclear antigen. The potential relation of these cells to hepatocytes which may serve as the principal reserve for replicating hepatocytes is discussed.     

Sex expression in EgyptianThymelaea hirsuta (Thymelaeaceae) populations

The sex expression inThymelaea hirsuta was assessed in five habitats in the western Mediterranean desert of Egypt. The survey over two main flowering periods indicated that the sexual expression of this plant is complex and labile. Beside the dioecious male and female states, five monoecious states were detected. The dioecious states are more abundant and less labile. There is a clear shift from monoecious towards dioecious states and in general favour of males from the first (late autumn) to the second (late winter) flowering period. These results are discussed in view of the adaptive theories and evolution.     

Modeling problems in conservation genetics using captive Drosophila populations: Consequences of equalizing founder representation

Equalizing founder representation is a recommended practice for maintaining captive populations. However, this procedure has not been subject to controlled experimental evaluation. The effects on inbreeding, genetic variation, and reproductive fitness of maintaining small captive populations by equalizing founder representation (EFR) versus randomly choosing parents (RC) were compared. Ten replicate lines were created with unequal founder representations, split into EFR and RC lines, and maintained for a further eight generations. Founder representations computed from pedigrees were closer to equality in the EFR lines than in the RC lines or the base population, most of the changes being evident after one generation. Significant benefits of EFR were found in lowered inbreeding (mean inbreeding coefficients of 0.35 and 0.41, respectively, for EFR and RC lines) and average heterozygosity (0.141 for EFR, 0.084 for RC, compared with 0.216 in the base population). However, EFR was not significantly better than RC in moving allele frequencies towards equalized founder representation. No significant difference was found in reproductive fitness between EFR and RC (relative fitnesses compared to the base population were 0.179 for EFR and 0.182 for RC). The use of equalization of founder representation for a few generations can be recommended in the genetic management of captive populations derived from a small number of founders that contribute unequally. © 1992 Wiley-Liss, Inc.     

Novel seed lipid phenotypes in combinations of mutants altered in fatty acid biosynthesis inArabidopsis

Summary The seed fatty acid (FA) composition of various single mutant combinations ofArabidopsis thaliana that affect FA biosynthesis has been examined. Double mutant combinations offae, a mutation affecting CIS elongation, and a series of four other FA biosynthetic mutants were synthesized. The four other single mutants were:fad2 andfad3, which are deficient in 181 and 182 desaturation, respectively;fab1, which is elevated in 160 and decreased in 181; andfab2, which is elevated in 180 and decreased in 181. The superimposition of two blocks in the FA biosynthetic pathway leads to dramatic changes in the FA content of the double mutants. The tenArabidopsis stocks analyzed to date (wild-type, five single mutants, and four double mutants) make seed oils with a wide range of FA compositions, and illustrate the diversity of oils it is possible to obtain from a single plant species.     

Expected utility maximization and selection of stable plant cultivars

Summary In most plant breeding programs, selection of the best commercially suitable cultivars for a target group of environments is based on information obtained from evaluation trials cultivated in a sample of environments. Information on the performance of cultivars collected in a sample of environments can only be approximate and, consequently, selection of the best cultivar involves choosing among cultivars that respond uncertainly in many environments. The agronomic and/or economic value of a cultivar across environments may be considered the general or overall utility of the cultivar. Data from a sample of environments therefore provides only an estimate of any cultivar's overall utility, with the overall goal of selection among all cultivars being the maximization of the expected utility. Within this frame-work, expected utility maximization, an approach to decision making that has been well developed in the disciplines of economics and statistics, can assist the plant breeder in making such decisions. This research was initiated (1) to determine how expected utility maximization might be used to develop indices that are useful for selecting broadly adapted plant cultivars, and (2) to determine how the breeder's preferences might affect choice of the best cultivar. The data used in this research were from USDA Regional Soybean Tests. The results indicated that expected utility maximization, which explicitly incorporates into the selection rule the plant breeder's preferences regarding stability, can be a useful aid in the selection of stable plant cultivars.