Effects of anti-peptide antibodies against the second extracellular loop of human M2 muscarinic acetylcholine receptors on transmembrane potentials and currents in guinea pig ventricular myocytes

The effects of anti-peptide antibodies against the second extracellular loop of human M2 muscarinic receptor on transmembrane potentials and currents in guinea pig single ventricular cells were analyzed using whole-cell patch clamp technique. These effects were compared with those of the muscarinic receptor agonists carbachol and acetylcholine. The antibodies shortened the action potential duration in a dose-dependent manner. By using a ramp or step rectangular pulse protocol, it was found that the antibodies increased the outward K⁺ current and decreased the inward basal I Ca significantly. The reversal potential of both carbachol-and antibody-induced extra currents were close to –80 mV, being in proximity to the calculated E_k of –90 mV. A -adrenergic receptor agonist, isoprenaline, prolonged the action potential and increased the overshoot which could be inhibited by both antibody and carbachol. Isoprenaline increased inward I_ca and outward I_k simultaneously. Both antibody and carbachol could significantly reduce the isoprenaline-stimulated I_Ca but not the isoprenaline-stimulated I_k. The antibody- or carbachol-induced outward K⁺ current and the depressant effects of antibody and carbachol on isoprenaline-stimulated I_ca were partially antagonized by atropine. These results suggest that the anti-M2 muscarinic receptor antibodies display a stimulatory activity similar to muscarinic receptor agonist on the receptor-mediated electrophysiological events.     

Reduction of cardiac hypertrophy in TGR(mREN2)27 by angiotensin II receptor blockade

TGR(mREN2)27 is a transgenic rat harboring the murine Ren-2 gene and exhibit fulminant hypertension and marked heart hypertrophy. In order to study the role of angiotensin II in the increase of cardiac mass, these animals were treated with anti-hypertensive and non-antihypertensive doses of the angiotensin II receptor AT₁ antagonist Telmisartan for 9 weeks. All doses led to significant reductions of heart hypertrophy detected by the evaluation of the diameter of cardiac muscle bundles. We conclude from this study that cardiac hypertrophy in TGR(mREN2)27 is characterized by an increased volume of cardiomyocytes and an unchanged amount of fibrous tissue and that angiotensin II plays an important role in the mechanisms leading to this phenotype.     

Shoot regeneration from tissue-cultured leaves of the American cranberry (Vaccinium macrocarpon)

A method for shoot regeneration from leaf explants in two cultivars of cranberry (Vaccinium macrocarpon Ait.) is described. Modified Anderson's medium supplemented with combinations of thidiazuron (TDZ) with or without 1 M NAA (-naphthaleneacetic acid) was used to optimize shoot regeneration. The effect of light or dark incubation was also determined. Maximum regeneration was obtained in the light in the presence of 10 M TDZ and 1 M NAA. While this medium was suitable for leaf explants obtained from shoot cultures, regeneration did not occur from leaves collected from greenhouse-grown plants. Elongation of the regenerated shoot tips did not occur until explants were transferred to growth regulator-free medium at which time only a minority of shoots elongated. Elongated shoots could be dissected away from leaf tissue, rooted easily, and acclimitized to ambient conditions.Abbreviations NAA -naphthaleneacetic acid - TDZ 1-phenyl-3-(1,2,3-thiadiazol-5-yl) urea     

Carbohydrate and carbon metabolite accumulation responses in leaves of ozone tolerant and ozone susceptible spinach plants after acute ozone exposure

The objective of this study was to determine whether exposure of plants to ozone (O₃) increased the foliar levels of glucose, glucose sources, e.g., sucrose and starch, and glucose-6-phosphate (G6P), because in leaf cells, glucose is the precursor of the antioxidant, L-ascorbate, and glucose-6-phosphate is a source of NADPH needed to support antioxidant capacity. A further objective was to establish whether the response of increased levels of glucose, sucrose, starch and G6P in leaves could be correlated with a greater degree of plant tolerance to O₃. Four commercially available Spinacia oleracea varieties were screened for tolerance or susceptibility to detrimental effects of O₃ employing one 6.5 hour acute exposure to 25O nL O₃ L^-1 air during the light. One day after the termination of ozonation (29 d post emergence), leaves of the plants were monitored both for damage and for gas exchange characteristics. Cultivar Winter Bloomsdale (cv Winter) leaves were least damaged on a quantitative grading scale. The leaves of cv Nordic, the most susceptible, were approximately 2.5 times more damaged. Photosynthesis (Pn) rates in the ozonated mature leaves of cv Winter were 48.9% less, and in cv Nordic, 66.2% less than in comparable leaves of their non-ozonated controls. Stomatal conductance of leaves of ozonated plants was found not to be a factor in the lower Pn rates in the ozonated plants. At some time points in the light, leaves of ozonated cv Winter plants had significantly higher levels of glucose, sucrose, starch, G6P, G1P, pyruvate and malate than did leaves of ozonated cv Nordic plants. It was concluded that leaves of cv Winter displayed a higher tolerance to ozone mediated stress than those of cv Nordic, in part because they had higher levels of glucose and G6P that could be mobilized during diminished photosynthesis to generate antioxidants (e.g., ascorbate) and reductants (e.g., NADPH). Elevated levels of both pyruvate and malate in the leaves of ozonated cv Winter suggested an increased availability of respiratory substrates to support higher respiratory capacity needed for repair, growth, and maintenance.Abbreviations ADPG-PPiase ADPglucose pyrophosphorylase - ASC L-ascorbic acid - APX ascorbate peroxidase - Ce CO₂ concentration in air in the measuring cuvette during photosynthesis measurements - Ci CO₂ concentration in the leaf intercellular spaces during photosynthesis measurement - Chl chlorophyll - DHA dehydroascorbic acid - DHA reductase dehydroascorbate reductase - DHAP dihydroxyacetone phosphate - GAP glyceraldehyde-3-phosphate - Gluc glucose - GR glutathione reductase - G_sw stomatal conductance with units as mmol H₂O m^-2 s^-1 - GSSG oxidized glutathione - GSH reduced glutathione - G1P glucose-1-phosphate - G6P glucose-6-phosphate - G6P dehydrogenase glucose-6-phosphate dehydrogenase - 6PG 6-phosphogluconate - 6PG dehydrogenase 6-phosphogluconate dehydrogenase - F6P fructose-6-phosphate - FBP fructose-1,6-bisphosphate - MAL malate - MDHA reductase monodehydroascorbate reductase - PE post-emergence - PEP phosphoenolpyruvate - PGA 3-phosphoglycerate - Pi orthophosphate - PYR pyruvate - Pn net CO₂ photoas-similation in leaves - PPFD photosynthetic photon flux density with units of mol photons m^-2 s^-1 - PPRC pentose phosphate reductive cycle - RuBP ribulose-1,5-bisphosphate - rubisco ribulose-1,5-bisphosphate carboxylase/oxygenase - SLW specific leaf weight - TCA cycle tricarboxylic acid cycle - Triose-P DHAP+GAP     

Members of two gene families encoding ubiquitin-conjugating enzymes, AtUBC1-3 and AtUBC4-6, fromArabidopsis thaliana are differentially expressed

Covalent attachment of ubiquitin to other intracellular proteins is essential for many physiological processes in eukaryotes, including selective protein degradation. Selection of proteins for ubiquitin conjugation is accomplished, in part, by a group of enzymes designated E2s or ubiquitin-conjugating enzymes (UBCs). At least six types of E2s have been identified in the plantArabidopsis thaliana; each type is encoded by a small gene family. Previously, we described the isolation and characterization of two three-member gene families, designatedAtUBC1-3 andAtUBC4-6, encoding two of these E2 types. Here, we investigated the expression patterns, of theAtUBC1-3 andAtUBC4-6 genes by the histochemical analysis of transgenicArabidopsis containing the corresponding promoters fused to the -glucuronidase-coding region. Staining patterns showed that these genes are active in many stages of development and some aspects of cell death, but are not induced by heat stress. Within the two gene families, individual members exhibited both overlapping and complementary expression patterns, indicating that at least one member of each gene family is expressed in most cell types and at most developmental stages. Different composite patterns of expression were observed between theAtUBC1-3 andAtUBC4-6 families, suggesting distinct biochemical and/or physiological functions for the encoded E2s inArabidopsis.     

Elongation factor 1α genes of the red alga Porphyra purpurea include a novel, developmentally specialized variant

The life cycle of the red alga Porphyra purpurea alternates between two morphologically distinct phases: a shell-boring, filamentous sporophyte and a free-living, foliose gametophyte. From a subtracted cDNA library enriched for sporophyte-specific sequences, we isolated a cDNA encoding an unusual elongation factor 1 (EF-1) that is expressed only in the sporophyte. A second EF-1 gene that is expressed equally in the sporophyte and the gametophyte was isolated from a genomic library. These are the only EF-1 genes detectable in P. purpurea. The constitutively expressed gene encodes and EF-1 very similar to those of most eukaryotes. However, the sporophyte-specific EF-1 is one of the most divergent yet described, with nine insertions or deletions ranging in size from 1 to 26 amino acids. This is the first report of a developmental stage-specific EF-1 outside of the animal kingdom and suggests a fundamental role for EF-1 in the developmental process.     

The extended replicator

This paper evaluates and criticises the developmental systems conception of evolution and develops instead an extension of the gene's eye conception of evolution. We argue (i) Dawkin's attempt to segregate developmental and evolutionary issues about genes is unsatisfactory. On plausible views of development it is arbitrary to single out genes as the units of selection. (ii) The genotype does not carry information about the phenotype in any way that distinguishes the role of the genes in development from that other factors. (iii) There is no simple and general causal criterion which distinguishes the role of genes in development and evolution. (iv) There is, however, an important sense in which genes but not every other developmental factor represent the phenotype. (v) The idea that genes represent features of the phenotype forces us to recognise that genes are not the only, or almost the only, replicators. Many mechanisms of replication are involved in both development and evolution. (vi) A conception of evolutionary history which recognises both genetic and non-genetic replicators, lineages of replicators and interactors has advantages over both the radical rejection of the replicator/interactor distinction and the conservative restriction of replication to genetic replication.     

Heuristic optimization of the general life history problem: A novel approach

Summary The general life history problem concerns the optimal allocation of resources to growth, survival and reproduction. We analysed this problem for a perennial model organism that decides once each year to switch from growth to reproduction. As a fitness measure we used the Malthusian parameterr, which we calculated from the Euler-Lotka equation. Trade-offs were incorporated by assuming that fecundity is size dependent, so that increased fecundity could only be gained by devoting more time to growth and less time to reproduction. To calculate numerically the optimalr for different growth dynamics and mortality regimes, we used a simplified version of the simulated annealing method. The major differences among optimal life histories resulted from different accumulation patterns of intrinsic mortalities resulting from reproductive costs. If these mortalities were accumulated throughout life, i.e. if they were senescent, a bangbang strategy was optimal, in which there was a single switch from growth to reproduction: after the age at maturity all resources were allocated to reproduction. If reproductive costs did not carry over from year to year, i.e. if they were not senescent, the optimal resource allocation resulted in a graded switch strategy and growth became indeterminate. Our numerical approach brings two major advantages for solving optimization problems in life history theory. First, its implementation is very simple, even for complex models that are analytically intractable. Such intractability emerged in our model when we introduced reproductive costs representing an intrinsic mortality. Second, it is not a backward algorithm. This means that lifespan does not have to be fixed at the begining of the computation. Instead, lifespan itself is a trait that can evolve. We suggest that heuristic algorithms are good tools for solving complex optimality problems in life history theory, in particular questions concerning the evolution of lifespan and senescence.