Parental effects in Pieris rapae in response to variation in food quality: adaptive plasticity across generations?

1. Herbivores using seasonal resources must cope with variation in the quality of their host plants. The effects of variation in protein concentration of artificial diet and glucosinolate concentration in canola, Brassica napus, on Pieris rapae parental and progeny growth were investigated. 2. The hypothesis that parents respond to variation in food quality by altering the phenotype of their progeny to enhance progeny fitness was tested. Consistent with previous studies, P. rapae was not affected strongly by variation in the protein concentration of artificial diet and had equal mass on completing development. 3. The mass of individual eggs of P. rapae progeny was correlated negatively with the amount of protein in the diet on which parents fed. Moreover, mothers reared in extreme conditions (high and low protein) produced progeny that grew best under those conditions. These potentially adaptive parental effects were detected early in progeny growth but not later in their development. 4. Early larval growth of P. rapae was affected negatively by increasing glucosinolates in B. napus plants, although no effects of glucosinolates were detected later in growth or on the progeny's phenotype. 5. Thus, evidence is presented that variation in food quality (protein concentration) has major consequences for the progeny of P. rapae. Given the multivoltine life history of P. rapae and the seasonal differences in food quality it encounters, such parental effects may be adaptive.     

Oxygen uptake rates in cultured rat hepatocytes

One potential treatment of acute liver failure involves the use of an extracorporeal device composed of functional hepatocytes. A major issue in the design of such a large-scale device is providing the hepatocytes with a sufficient supply of oxygen and other nutrients. In this study, we have designed and characterized a simple perfusion system hepatocytes using this system. The OUR of hepatocytes was determined during the first day after seeding on a single collagen gel and during the long-term stable culture after the addition of a top layer of collagen. The OUR increased to 20.7 +/- 0.57 pmol/sec/mug DNA during the first 13 hours of culture on a single collagen gel, while during the next 11 hours, the OUR declined to 10.6 +/- 1.5 pmol/sec/mug DNA. In parallel with the increase in OUR during the first 10 hours, we observed significant cell spreading, suggesting that the oxygen supply to the cells may be critical for the spreading and adaptation of the anchorage-dependent hepatocytes following isolation. Addition of a top layer of collagen to hepatocyte cultures for 24 hours of culture on a single collagen layer resulted in a stable OUR for 15 days. These results indicate that OUR of hepatocytes in culture may vary depending on the phase of culture (i.e., early vs. late) and on the extracellular environment. (c) 1992 John Wiley & Sons, Inc.     

Treatment of human cell lines with 5-azacytidine may result in profound alterations in clonogenicity and growth rate

Liquid medium cultures of three human cell lines (B-lymphoma, myeloma, and squamous lung carcinoma) with population-doubling times (PDT) and cloning efficiencies (CE) in the range of 32-43 h and 0.01-5.6%, respectively, were exposed to 5-azacytidine (5-azaC) for 3 d. The doses used (1-3 microM) were found to be nontoxic as measured by cell growth in liquid and semisolid agar medium and to be nonmutagenic as measured by the rate of generation of ouabain- and 6-thioguanine-resistant cell variants. After 5-azaC treatment, cell samples were subsequently harvested every day and assayed for their CE in semisolid agar medium. For each cell line, 30 to 42 individual clones were harvested at the day of maximal CE and expanded in liquid culture medium. PDT and CE were determined for each subclone about every 6 wk for 12 mo. The majority of the subclones had unaltered PDT and CE compared to the original lines. However, several clones had profoundly changed proliferative activity with PDT on approximately 12-14 h and/or CE 5 to greater than 50%. Some of the clones with altered growth properties reverted to PDT and/or CE values of untreated clones. However, a few clones of each line had stable alterations with PDT on 12-14 h and CE 5 to greater than 50%; these clones were all significantly hypomethylated. It is concluded that the human gene repertoire does contain genes that appropriately activated can result in growth properties with very short PDT and high CE (and comparable to animal cell lines), and that this activation may be obtained by 5-azaC treatment. It is conceivable that the procedure here described to alter growth properties of human cell lines may be applied to experimental situations, where alterations of cell growth properties are desired.     

Induction of urokinase-type plasminogen activator by UV light in human fetal fibroblasts is mediated through a UV-induced secreted protein.

Plasminogen activator was previously shown to be induced by UV light in human cells with low capacity to repair UV-induced DNA lesions. We now show that in human fetal fibroblasts UV light enhanced the two mRNA species coding for the urokinase-type plasminogen activator (uPA) and the tissue-type plasminogen activator, but immunological analysis revealed exclusively uPA activity. Several independent and complementary experiments indicated that induction of uPA was mediated, apparently entirely, through a UV-induced, secreted protein (UVIS) in the growth medium of irradiated cells. First, elevation of uPA mRNA after irradiation was severely blocked by cycloheximide. Second, replacement of conditioned medium in irradiated cells while the rate of plasminogen activator induction was maximal rapidly and completely stopped any further increase in uPA activity. Third, addition of the same removed conditioned medium to nonirradiated cells mimicked UV light in enhancing the level of uPA activity as well as that of uPA mRNA. Fourth, UVIS activity was completely lost by treating the conditioned medium with trypsin but not with nucleases. Kinetic measurements indicated that the accumulation of UVIS rather than the induction of uPA by UVIS conferred the rate-limiting step in the overall process of uPA induction. Both UV light and UVIS acted synergistically with inhibitors of DNA repair for uPA induction. Based on these results, a model is proposed implicating relaxation of DNA torsional stress of an as yet undefined DNA sequence(s) in the induction of UVIS, which is then responsible for activation of the uPA gene.     

Regional differences in cholinergic regulation of potassium current in feline esophageal circular smooth muscle

Potassium channels are important contributors to membrane excitability in smooth muscles. There are regional differences in resting membrane potential and K(+)-channel density along the length of the feline circular smooth muscle esophagus. The aim of this study was to assess responses of K(+)-channel currents to cholinergic (ACh) stimulation along the length of the feline circular smooth muscle esophageal body. Perforated patch-clamp technique assessed K(+)-channel responses to ACh stimulation in isolated smooth muscle cells from the circular muscle layer of the esophageal body at 2 (distal)- and 4-cm (proximal) sites above the lower esophageal sphincter. Western immunoblots assessed ion channel and receptor expression. ACh stimulation produced a transient increase in outward current followed by inhibition of spontaneous transient outward currents. These ACh-induced currents were abolished by blockers of large-conductance Ca(2+)-dependent K(+) channels (BK(Ca)). Distal cells demonstrated a greater peak current density in outward current than cells from the proximal region and a longer-lasting outward current increase. These responses were abolished by atropine and the specific M(3) receptor antagonist 4-DAMP but not the M(1) receptor antagonist pirenzipine or the M(2) receptor antagonist methoctramine. BK(Ca) expression along the smooth muscle esophagus was similar, but M(3) receptor expression was greater in the distal region. Therefore, ACh can differentially activate a potassium channel (BK(Ca)) current along the smooth muscle esophagus. This activation probably occurs through release of intracellular calcium via an M(3) pathway and has the potential to modulate the timing and amplitude of peristaltic contraction along the esophagus.     

A new species of Sphaeromyxa (Myxosporea: Sphaeromyxina: Sphaeromyxidae) in devil firefish, Pterois miles (Scorpaenidae), from the northern Red Sea: morphology, ultrastructure, and phylogeny

Sphaeromyxa zaharoni n. sp. (Myxosporea) is described from the gallbladder of devil firefish, Pterois miles (Scorpaenidae), from coral reefs of the Gulf of Eilat, Israel, northern Red Sea. The parasite was found also in bearded scorpionfish, Scorpaenopsis barbata, from the same area. This is the first report on Sphaeromyxa sp. from this zoogeographical region. The plasmodia are amoeboid when young, becoming disc-shaped and elongated when mature. In paraffin sections, the plasmodium periphery appears as a finely granulated, strongly eosinophilic layer with an intricate surface membrane network. Sphaeromyxa zaharoni n. sp. is polysporous, disporoblastic, and has asynchronous sporogenesis. The mature spore is elongated and fusiform, has delicately ridged valves, and contains a single, binucleated sporoplasm. In valvular view, the tips are truncated. The mean spore size is length 14.5 microm, width 4.8 microm, and polar capsule 4.8 x 3.4 microm. The 2 equally sized ovoid polar capsules are positioned at opposite ends of the spore, each containing a filament loosely folded in 2 loops. The fine structure of the sporoblast and spore corresponded with previously studied Sphaeromyxa species. According to small-subunit ribosomal DNA gene sequence analysis, S. zaharoni n. sp. is most closely related to 2 Myxidium spp. The close phylogenetic relatedness of Sphaeromyxa and Myxidium and similar spore morphology raises the question whether these 2 genera should be maintained in separate families and suborders.     

The effect of intestinal anaphylaxis on postprandial motility in the rat

We have previously utilized a rat animal model to demonstrate that challenge of fasted sensitized animals with antigenic food protein is associated with diarrhea and altered intestinal myoelectric and motor activities. In this paper we examine the effect of intestinal anaphylaxis on postprandial motility in the same animal model. Hooded Lister rats were sensitized (S) by intraperitoneal injection of 10 micrograms egg albumin (i.e., antigen (Ag) and compared with sham-sensitized controls (C). Seven days later, three bipolar jejunal electrodes and a jejunostomy tube, for motility recording and Ag administration, were implanted. On day 14, intestinal myoelectric and motor activities were measured in fed animals before and after intraluminal challenge with Ag (100 mg egg albumin/0.5 mL saline) or placebo (P; 0.5 mL saline). Specific immunoglobulin E serum titres were greater than or equal to 1:64 in S animals, while C animals showed no response. None of the C animals challenged with P or Ag and none of the S animals challenged with P defecated after challenge, but all the S animals challenged with Ag developed diarrhea (p less than 0.001). There was no disruption or alteration of the fed motility pattern in C animals challenged with P or Ag, or S animals challenged with P. In fed S animals challenged with Ag the fed motility pattern persisted, but there was a significant (p less than 0.05) increase in the number of high-amplitude aborally propagating clustered contractions, where the phasic contractile activity was superimposed on a sustained tonic elevation of intraluminal pressure lasting 5-10 s.(ABSTRACT TRUNCATED AT 250 WORDS)     

Bacterial predator–prey dynamics in microscale patchy landscapes

Soil is a microenvironment with a fragmented (patchy) spatial structure in which many bacterial species interact. Here, we explore the interaction between the predatory bacterium Bdellovibrio bacteriovorus and its prey Escherichia coli in microfabricated landscapes. We ask how fragmentation influences the prey dynamics at the microscale and compare two landscape geometries: a patchy landscape and a continuous landscape. By following the dynamics of prey populations with high spatial and temporal resolution for many generations, we found that the variation in predation rates was twice as large in the patchy landscape and the dynamics was correlated over shorter length scales. We also found that while the prey population in the continuous landscape was almost entirely driven to extinction, a significant part of the prey population in the fragmented landscape persisted over time. We observed significant surface-associated growth, especially in the fragmented landscape and we surmise that this sub-population is more resistant to predation. Our results thus show that microscale fragmentation can significantly influence bacterial interactions.