Escherichia coli K12 does not colonize the gastrointestinal tract of Fischer-344 rats

Summary The colonizing potential ofEscherichia coli K12 containing a vector coding for somidobove (bovine somatotropin) was determined. Treated male and female Fischer-344 rats were given a single oral gavage inoculum of sucrose with/without tetracycline (15 g/ml). Untreated control animals received similar drinking water regimes. All animals survived until termination. There were no clinical signs of toxicity observed and no treatment-related effect upon body weight, food consumption, or efficiency of food utilization. Fresh fecal samples were collected from each rat every 24 h following inoculation and the population of the marked strain was quantitated until no bacterial colonies were observed for two consecutive days. While all inoculated rats were positive at 24 h, by 72 and 96 h all had become negative for the test (marked) strain, as were the corresponding control group throughout the test. The frozen stock of the marked strain used as the positive control demonstrated that the agar plates were selective for the test strain. Fourteen days following inoculation, all groups of rats were killed and the gastrointestinal tracts removed and treated to recover the marked strain. There was no evidence of the marked strain in the gastrointestinal tract of any rat from any group. Thus, theE. coli K12 host/vector system used in this experiment does not colonize the gastrointestinal tract of Fischer-344 rats.     

Access to coronary catheterisation: fair shares for all?

OBJECTIVE--To determine the effects of patient''s sex and area''s material deprivation on utilisation rates of coronary catheterisation and angiography in the investigation of ischaemic heart disease. DESIGN--Retrospective analysis of routinely collected hospital statistics. SETTING--Acute hospitals throughout Northern Ireland. SUBJECTS--24,179 episodes of patients discharged from hospital with a primary diagnosis of ischaemic heart disease and 1270 episodes relating to patients with an underlying diagnosis of ischaemic heart disease who had either coronary catheterisation or angiography. MAIN OUTCOME MEASURES--Age standardised admission rates for heart disease and age standardised utilisation rates for catheterisation or angiography, or both, for 566 electoral wards ranked by Townsend "deprivation" scores. RESULTS--Catheterisation-angiography rates in men were over fivefold those of women, ranging from 85.5/100,000 v 16/100,000 in patients from "well off" areas to 123/100,000 v 22/100,000 for patients from deprived areas. After admission rates for heart disease were controlled for, the overall rate ratio for women was 0.48 (95% confidence interval 0.38 to 0.60). After differential admission rates for heart disease and other potential clinical confounders were controlled for, the investigation rates of patients from the least and most "deprived" areas were not significantly different (rate ratio 1.04 (0.87 to 1.25)). CONCLUSION--Although investigation rates were significantly lower in women than in men, further clinical data would be required before labelling this underutilisation as evidence of bias. There was no significant difference in invasive investigation rates for heart disease in areas of varying deprivation or affluence.     

Proteomics in Drosophila melanogaster.

To be able to understand cellular mechanisms, we require fully integrated data sets combining information about gene expression, protein expression, post-translational modification states, sub-cellular location and complex formation. Proteomics is a very powerful technique that can be applied to interrogate changes at the protein level. Studying this effectively requires specialised facilities within research institutes. Here, we describe the setting up and operation of such a facility, providing a resource for the Arabidopsis and Drosophila research communities.     

Cytokinins and bud morphology in Pinus radiata

Cytokinins (CKs) play essential roles in the regulation of plant growth and development. In the previous paper (Zhang et al. 2001), we reported the detection and identification of a wide spectrum of CKs, including several novel forms, in the buds of Pinus radiata D. Don. In this paper we examine the relationship between the CKs and buds from juvenile and adult trees of P. radiata. During development the morphology of buds alters significantly, from buds bearing primary needles during their juvenile phase to buds sealed in scales at the adult phase. The morphology of adult buds is a very stable character, as fascicle meristems released from apical dominance, or cultured in vitro, produced only secondary needles. However, exogenous CK causes the adult buds to revert to juvenile bud development in vitro . Analyses of the endogenous CKs revealed that juvenile buds had a relatively higher level of isopentenyladenine and isopentenyladenosine, extremely low levels of phosphorylated CKs and a relatively low level of novel CK glycosides. The adult buds contained lower levels of free base and riboside CKs but very high levels of phosphorylated CKs and novel CK glycosides. Possible roles for CKs in the regulation of bud development are discussed.     

Predicting chlorophyll vertical distribution in response to epilimnetic nutrient enrichment in small stratified lakes

Light-limited metalimnetic phytoplankton communities are thoughtto be negatively impacted by epilimnetic nutrient enrichmentbecause of shading by increased epilimnetic phytoplankton biomass.We tested this expectation with a dynamic simulation model thatwas calibrated to three lakes undergoing whole-lake nutrientand food web manipulations. Total areal chlorophyll increaseddue to nutrient enrichment in each lake, but the magnitude ofthe response varied between lakes. Modeling experiments, whichallowed analysis of separate components of each lake's responseto nutrient enrichment, indicated that the response to enrichmentdepended on lake water color and food web structure. In weaklystained lakes ({small tilde}10 mg Pt 1^–1, k₄ = 0.4 m^–1),metalimnetic chlorophyll was stimulated by nutrient enrichmentup to moderate levels (1 µg Pt1^–1 day^–1).In more strongly colored lakes (25 mg Pt 1^–1, k₄ = 1.0),metalimnetic chlorophyll responded negatively to nutrient enrichmentat all P loading rates. Food web structure, as expressed byrates of zooplanktivory, interacted with water color in twoways. One impact was through direct grazing losses on metalimneticchlorophyll. The other process involved was indirect impactfrom grazing on epilimnetic phytoplankton, which reduced shadingon metalimnetic chlorophyll. Vertical redistribution of chlorophyllbetween the epilimnion and the metalimnion led to little accumulationof areal chlorophyll with increased P loading over limited rangesof water color and nutrient input rates. Model predictions maybe most effectively tested with whole-lake experiments contrastingfood web structure, water color and nutrient loading.     

Changes of Respiratory Chain Activity in Mitochondrial and Synaptosomal Fractions Isolated from the Gerbil Brain After Graded Ischaemia

Abstract: In this study we have examined (1) the integrated function of the mitochondrial respiratory chain by polarographic measurements and (2) the activities of the respiratory chain complexes I, II–III, and IV as well as the ATP synthase (complex V) in free mitochondria and synaptosomes isolated from gerbil brain, after a 30-min period of graded cerebral ischaemia. These data have been correlated with cerebral blood flow (CBF) values as measured by the hydrogen clearance technique. Integrated functioning of the mitochondrial respiratory chain, using both NAD-linked and FAD-linked substrates, was initially affected at CBF values of ∼35 ml 100 g⁻¹ min⁻¹, and declined further as the CBF was reduced. The individual mitochondrial respiratory chain complexes, however, showed differences in sensitivity to graded cerebral ischaemia. Complex I activities decreased sharply at blood flows below ∼30 ml 100 g⁻¹ min⁻¹ (mitochondria and synaptosomes) and complex II–III activities decreased at blood flows below 20 ml 100 g⁻¹ min⁻¹ (mitochondria) and 35–30 ml 100 g⁻¹ min⁻¹ (synaptosomes). Activities declined further as CBF was reduced below these levels. Complex V activity was significantly affected only when the blood flow was reduced below 15–10 ml 100 g⁻¹ min⁻¹ (mitochondria and synaptosomes). In contrast, complex IV activity was unaffected by graded cerebral ischaemia, even at very low CBF levels.     

EGF receptor-mediated signals are differentially modulated by concanavalin A

NIH 3T3 cells expressing hgh levels of the human epidermal growth factor (EGF) receptor were used to examine the effects of the lectin concanavalin A (Con A) on EGF-mediated signaling events. Proliferation of NIH 3T3 cells expressing high levels of the human EGF receptor was inhibited in a dose-dependent manner by Con A. At the same time, Con A also inhibited both dimerization and tyrosine phosphorylation of the EGF receptor. Tyrosine phosphorylation of the enzyme phospholiphase C-γ, a substrate of the phosphorylated EGF receptor kinase, was also inhibited. In contrast, EGF-stimulated changes in pH, calcium, and levels of inositol phosphates were unaffected by the presence of Con A. These results indicate that certain signals (changes in the levels of intracellular calcium, pH, and inositol phosphates) mediated by EGF binding to its receptor still occur when receptor dimerization and phosphorylation are dramatically decreased, suggesting that multiple independent signals are transmitted by the binding of EGF to its receptor. © 1995 Wiley-Liss, Inc.     

Metabolic inhibitors induce symplastic movement of solutes from the transport phloem of Arabidopsis roots

The distribution of the phloem-mobile fluorescent probe carboxyfluorescein(CF) within the primary root of Arabidopsis thaliana was imagedusing a confocal laser scanning microscope (CLSM) and the tissueand subcellular distribution of the probe was shown to be influencedby treatment with a number of metabolic inhibitors. Sodium azidecompletely inhibited the phloem transport of CF into the treatedregion of root. Treatment with both CCCP and probenecid inducedthe lateral movement of CF from the transport phloem to theadjacent cell layers, and the probe accumulated in the cytoplasmof the pericycle, endodermis, cortex, and epidermis. This lateraltransfer of CF was restricted to the pericycle in the presenceof plasmolysing concentrations of sorbitol. Ultrastructuralinvestigations demonstrated the presence of a plasm odesmatalpathway leading from the sieve elementcompanion cell complex(SE-CC) out into the cortex. The results are consistent withthe operation of this symplastic pathway under conditions ofmetabolic energy reduction and are discussed in relation tothe regulation of plasmodesmatal conductance in the transportphloem. Key words: Arabidopsis, confocal laser scanning microscopy (CLSM), metabolic inhibitors, phloem transport, symplastic phloem unloading     

Response of compressed skinned skeletal muscle fibers to conditions that simulate fatigue

Myburgh, Kathryn H., and Roger Cooke. Response ofcompressed skinned skeletal muscle fibers to conditions that simulate fatigue. J. Appl. Physiol. 82(4):1297-1304, 1997.During fatigue, muscles become weaker, slower,and more economical at producing tension. Studies of skinned musclefibers can explain some but not all of these effects, and, inparticular, they are less economical in conditions that simulatefatigue. We investigated three factors that may contribute to thedifferent behavior of skinned fibers. 1) Skinned fibers have increasedmyofilament lattice spacing, which is reversible by osmoticcompression. 2) A myosin subunit becomes phosphorylated during fatigue.3) Inosine 5-monophosphate (IMP) accumulates during fatigue. We tested the response ofphosphorylated and unphosphorylated single skinned fibers (isometrictension, contraction velocity, and adenosinetriphosphatase activity) to changes in lattice spacing (0-5% dextran) and IMP (0-5 mM)in the presence of altered concentrations ofP_i (3-25 mM),H⁺ (pH 7-6.2), and ADP(0-5 mM). The response of maximally activated skinned fibers tothe direct metabolites of ATP hydrolysis is not altered by osmoticcompression, phosphorylating myosin subunits, or increasing IMPconcentration. These factors, therefore, do not explain the discrepancybetween intact and skinned fibers during fatigue.