Chimeras for mutations induced in dormant tomato seeds

Genetic chimeras of the VFNT cherry tomato line (Lycopersicon esculentum) were produced by mutagenizing seeds with ethyl methane sulfonate (EMS). The chimeras thereby produced were evaluated by progeny-testing the fruits of the genetically mosaic tissue. A total of 2011 M₁ plants was grown from treated seeds and evaluated by screening their 95175 (M₂) progeny for mutations affecting seedling phenotype. Three vigorous and fertile M₁ plants bearing mutant progeny with definitive phenotypes were selected for systematic harvesting and analysis. The specific location of each fruit was noted at harvest time, enabling the mutated sporogenous tissue of the mosaic M₁ plants to be traced. Sectoring appeared in both branch and floral tissues. In several cases, mutant progenies were restricted to individual branches or parts thereof. True-breeding recessive mutants whose monogenic mode of inheritance was later established occasionally segregated within M₁ fruit progenies at frequencies that indicate a non-homogeneous floral meristem origin. The data emphasize the necessity of making a well-distributed harvest of mosaic plants in order to detect as many variants as possible, as mosaic sectors may or may not recur late in ontogeny and may not contribute to sporogenous tissue early in development.     

Neutrophil polarisation in plasma differs to that induced by endogenous chemoattractants with regard to frequency of uropod formation and requirement for divalent cations.

Human neutrophils suspended in Hanks' balanced salt solution (37° C, 20 mM Hepes, pH 7.2) produced extensions, elongated and developed a polarised morphology with both a pseudopod and uropod when exposed to C5a (10 nM), leukotriene B4 (10 nM), platelet activating factor (40 nM) or interleukin-8 (12.5 nM). Responses to each mediator were generally enhanced or unaffected by chelators of extracellular Ca²⁺ and Mg²⁺. Neutrophils suspended in heparinised plasma (90-10% v/v in Hanks' balanced salt solution) produced extensions, elongated and developed a pseudopod, but rarely developed a uropod unless additional Mg²⁺ ions (0.5-5 mM) were added. These findings demonstrate that the polarisation of neutrophils in plasma is significantly different to that induced by endogenous chemoattractants with regard to the frequency of uropod formation and requirement for extracellular divalent cations.     

Effects of chemical speciation in growth media on the toxicity of mercury(II).

The toxicity of metals, including mercury, is expressed differently in different media, and the addition of soluble organics to the growth medium can have a significant impact on bioassay results. Although the effect of medium composition on metal toxicity is generally attributed to its effect on metal speciation (i.e., the chemical form in which the metal occurs), the importance of individual metal-ligand species remains largely unclear. Here, we report the results of a study that investigated, both experimentally and from a modeling perspective, the effects of complex soluble organic supplements on the acute toxicity (i.e., 50% inhibitory concentration [IC50]) of mercury to a Pseudomonas fluorescens isolate in chemically well-defined synthetic growth media (M-IIX). The media consisted of a basal inorganic salts medium supplemented with glycerol (0.1%, vol/vol) and a variety of common protein hydrolysates (0.1%, vol/vol), i.e., Difco beef extract (X = B), Casamino Acids (X = C), peptone (X = P), soytone (X = S), tryptone (X = T), and yeast extract (X = Y). These were analyzed to obtain cation, anion, and amino acid profiles and the results were used to compute the aqueous speciation of Hg(II) in the media. Respirometric bioassays were performed and IC50s were calculated. Medium components varied significantly in their effects on the acute toxicity of Hg(II) to the P. fluorescens isolate. IC50s ranged from 1.48 to 14.54 micrograms of Hg ml-1, and the acute toxicity of Hg(II) in the different media decreased in the order M-IIC >> M-IIP > M-IIB >> M-IIT > M-IIS >>> M-IIY.(ABSTRACT TRUNCATED AT 250 WORDS)     

Environmental vibrio phage–bacteria interaction networks reflect the genetic structure of host populations

Phages depend on their bacterial hosts to replicate. The habitat, density and genetic diversity of host populations are therefore key factors in phage ecology, but our ability to explore their biology depends on the isolation of a diverse and representative collection of phages from different sources. Here, we compared two populations of marine bacterial hosts and their phages collected during a time series sampling program in an oyster farm. The population of Vibrio crassostreae, a species associated specifically to oysters, was genetically structured into clades of near clonal strains, leading to the isolation of closely related phages forming large modules in phage–bacterial infection networks. For Vibrio chagasii, which blooms in the water column, a lower number of closely related hosts and a higher diversity of isolated phages resulted in small modules in the phage–bacterial infection network. Over time, phage load was correlated with V. chagasii abundance, indicating a role of host blooms in driving phage abundance. Genetic experiments further demonstrated that these phage blooms can generate epigenetic and genetic variability that can counteract host defence systems. These results highlight the importance of considering both the environmental dynamics and the genetic structure of the host when interpreting phage–bacteria networks.     

Homologous and heterologous regulation of the helodermin/vasoactive-intestinal-peptide response in the murine radiation leukemia-virus-induced lymphoma cell line BL/VL3

1. Functional vasoactive intestinal peptide (VIP)/helodermin receptors and beta 2-adrenoceptors coexist in membranes from a cultured cloned BL/VL3 cell line of murine T-cell lymphoma induced by a radiation leukemia virus (see preceding paper in this journal). 2. Short-term (5-30 min) exposures of BL/VL3 cells to VIP or isoproterenol induced both homologous and heterologous desensitization. The potency of VIP and isoproterenol to desensitize was similar to their potency to occupy receptors and activate adenylate cyclase. 3. Long-term (16-h) exposure of BL/VL3 cells to VIP induced homologous down regulation only, whereas isoproterenol induced both homologous and heterologous down regulation. The potency of VIP, peptide histidine isoleucinamide, helodermin, helospectin, and [D-Phe2]VIP on the one hand, and of isoproterenol on the other hand, to decrease homologous responses was comparable to their potency for receptor occupancy and adenylate cyclase activation.     

Lower Devonian Polyplacophora from New South Wales, Australia

Silicified polyplacophorans are common in the Lower Devonian Garra Formation in New South Wales. Four taxa occur within the lower 237 m of the formation at 14 horizons associated with an abundant and diverse fauna. Chelodes calceoloides Etheridge ranges through the section. New taxa are Chelodes cordatus sp. nov., Acutichiton depressolatus sp. nov., and Jugochiton patulus gen. and sp. nov. A single plate of an indeterminate genus occurs in the lower portion of the Camelford Limestone.     

USE OF A PETHIDINE AND MIDAZOLAM COMBINATION FOR THE REVERSIBLE SEDATION OF CRABEATER SEALS (LOBODON CARCINOPHAGUS)

Between October and December of 1996–1999, off eastern Antarctica (60°-150°E), we darted 31 crabeater seals with midazolam and pethidine at estimated dose rates of 0.15–0.4 mg/kg and 1–3 mg/kg, respectively. Maximum sedation was reached at 23 ± 9 min (n = 18) and first signs of recovery were noted at 54 ± 24 min (n = 4). Seals greater than 250 kg body-mass were sedated by administration of approximately 90–100 mg midazolam and 600 mg pethidine, but the degree of sedation was unpredictable and did not permit invasive procedures in some cases. Behavior of the seal and adjacent conspecifics affected the success of procedures and our ability to monitor vital signs. Naloxone and flumazenil reversed sedation, making this combination attractive for use in animals adjacent to water. Additional ketamine was administered to two seals, resulting in improved restraint.     

Effect of heat stress on glucose kinetics during exercise

Hargreaves, Mark, Damien Angus, Kirsten Howlett, Nelly MarmyConus, and Mark Febbraio. Effect of heat stress on glucose kinetics during exercise. J. Appl.Physiol. 81(4): 1594-1597, 1996.To identify themechanism underlying the exaggerated hyperglycemia during exercise inthe heat, six trained men were studied during 40 min of cyclingexercise at a workload requiring 65% peak pulmonary oxygen uptake(O_{2 peak}) on twooccasions at least 1 wk apart. On one occasion, the ambient temperaturewas 20°C [control (Con)], whereas on the other, it was40°C [high temperature (HT)]. Rates ofglucose appearance and disappearance were measured by using a primedcontinuous infusion of[6,6-²H]glucose. Nodifferences in oxygen uptake during exercise were observed betweentrials. After 40 min of exercise, heart rate, rectal temperature,respiratory exchange ratio, and plasma lactate were all higher in HTcompared with Con (P < 0.05). Plasmaglucose levels were similar at rest (Con, 4.54 ± 0.19 mmol/l; HT,4.81 ± 0.19 mmol/l) but increased to a greater extent duringexercise in HT (6.96 ± 0.16) compared with Con (5.45 ± 0.18;P < 0.05). This was the result of ahigher glucose rate of appearance in HT during the last 30 min ofexercise. In contrast, the glucose rate of disappearance and metabolicclearance rate were not different at any time point during exercise.Plasma catecholamines were higher after 10 and 40 min of exercise in HTcompared with Con (P < 0.05),whereas plasma glucagon, cortisol, and growth hormone were higher in HTafter 40 min. These results indicate that the hyperglycemia observedduring exercise in the heat is caused by an increase in liver glucoseoutput without any change in whole body glucoseutilization.