Muscle-like Arrays in a Fibroblast Line

SEVERAL investigators have speculated that the basis for all cellular contractile activity resides in a common molecular mechanism involving an interaction between actin and myosin^1–4. Thin filaments resembling the actin filaments of muscle have indeed been widely observed^3–5 and the recent demonstrations of heavy meromyosin binding to thin filaments^4–6 suggest that these ubiquitous filaments are, in fact, actin. Although muscle-like thick filaments have not been observed in non-muscle cells, myosin thick filaments have been reconstituted from blood platelet preparations¹. To our knowledge, however, no one has presented evidence for the natural occurrence of ordered arrays of thick and thin filaments in non-muscle cells.     

QUESTIONNAIRE PRACTICE: WHAT HAPPENS WHEN THE JAR SCALE IS PLACED BETWEEN TWO “OVERALL” ACCEPTANCE SCALES?

ABSTRACT

Using the observational analysis of two different foods as test products, this note examined some interesting findings that emerge when the just‐about‐right (JAR) scale was placed after the overall liking rating, and before the preference ranking. The JAR data appeared to be statistically uncorrelated with the overall rating scales. First, this fortuitous observation from several studies suggests that the JAR scale can play a diagnostic role to determine how the consumer feels about changing the product. Second, the statistical analysis of the JAR ratings (e.g., bipolar nature of the JAR scale, its skewness and kurtosis) all suggest that the appropriate measure is %JAR, an incidence metric, rather than scale average, ought to be used both to report the results, and to create models relating to the JAR versus sensory magnitude or versus liking, respectively.

PRACTICAL APPLICATIONS

The results of the present analysis suggest that overall acceptance/liking can be the last question in the questionnaire design. That location is very important for the sensory analysis of foods eaten over time and then rated, as well as personal care and cosmetic studies where the products are used over time periods, and where the true evaluation of performance ought to be made at the end of the trial. In these long‐term uses, overall liking is generally the last question given at the end of the time period of product evaluation. The facts that the just‐about‐right (JAR) scales are independent of this final overall liking rating suggest that the integrity of the overall evaluation and usefulness of JAR as diagnostics will not be compromised.     

The mosquito Anopheles (Cellia) oreios sp. n., formerly species 6 of the Australasian Anopheles farauti complex,and a critical review of its biology and relation to disease

Species 6 of the Australasian Anopheles farauti sibling species complex (Diptera: Culicidae) is described and formally named Anopheles oreios Bangs & Harbach, sp. n. Adult, pupal and fourth‐instar larval specimens collected in the Baliem Valley, Papua Province, Indonesia, are characterized and compared with those of Anopheles farauti, Anopheles hinesorum, Anopheles irenicus and Anopheles torresiensis (formerly informally denoted as species 1, 2, 7 and 3, respectively). The variable wings of adult females, the male genitalia, the pupa and the fourth‐instar larva of An. oreios are illustrated and DNA sequence data are included for regions coding for sections of the mitochondrial COI and COII genes. The biology of An. oreios and its relation to malaria transmission are discussed in detail and contrasted with the biology and disease relations of some members of the An. farauti and Anopheles punctulatus sibling species complexes.     

On the 13C/12C isotopic signal of day and night respiration at the mesocosm level

While there is currently intense effort to examine the ¹³C signal of CO₂ evolved in the dark, less is known on the isotope composition of day‐respired CO₂. This lack of knowledge stems from technical difficulties to measure the pure respiratory isotopic signal: day respiration is mixed up with photorespiration, and there is no obvious way to separate photosynthetic fractionation (pure c_i/c_a effect) from respiratory effect (production of CO₂ with a different δ¹³C value from that of net‐fixed CO₂) at the ecosystem level. Here, we took advantage of new simple equations, and applied them to sunflower canopies grown under low and high [CO₂]. We show that whole mesocosm‐respired CO₂ is slightly ¹³C depleted in the light at the mesocosm level (by 0.2–0.8‰), while it is slightly ¹³C enriched in darkness (by 1.5–3.2‰). The turnover of the respiratory carbon pool after labelling appears similar in the light and in the dark, and accordingly, a hierarchical clustering analysis shows a close correlation between the ¹³C abundance in day‐ and night‐evolved CO₂. We conclude that the carbon source for respiration is similar in the dark and in the light, but the metabolic pathways associated with CO₂ production may change, thereby explaining the different ¹²C/¹³C respiratory fractionations in the light and in the dark.     

Carbon balance during CAM: an assessment of respiratory CO2 recycling in the epiphytic bromeliads Aechmea nudicaulis and Aechmea fendleri

Abstract The regulation of crassulacean acid metabolism (CAM) under controlled environmental conditions has been investigated for two tropical epiphytes, relating plant water and carbon balance to growth form and habitat preference under natural conditions. Aechmea fendleri is restricted to wet, upper montane regions of Trinidad, while A. nudicaulis has a wider distribution extending into more arid regions of the island. Morphological characteristics of these plants are related to habitat preference in terms of leaf succulence (0.44 and 0.94 kg m^?2 for the two species respectively) and a distinct layer of water storage parenchyma in A. nudicaulis In contrast, the thinner leaves of A. fendleri contain little water-storage parenchyma and less chlorenchyma per unit area, but the plants have a more open leaf rosette. The two species differ in expression of CAM, since the proportion of respiratory CO₂ recycled as part of CAM had been found to be much lower in A. fendleri This study compared the efficiency of water use and role of respiratory CO₂ recycling under two PAR regimes (300 and 120 μnol m^?2 s^?1) and three night temperatures (12, 18 and 25 °C). Dark CO₂ uptake rates for both species were comparable to plants in the field (maximum of 2.3 ± 0.2 μmol m^?2s^?1± SD, n= 3). Total net CO₂ uptake at night increased on leaf area basis with temperature for both species under higher PAR, although under the low PAR regime CO₂ uptake was maximal at 18 °C. Water-use efficiency (WUE) increased at 18 °C and 25 °C during dark CO₂ uptake (Phase I) and also during late afternoon photosynthesis (Phase IV) in both species. For A. fendleri, dawn to dusk changes in titrable acidity (ΔH ⁺) were similar under high and low PAR, although ΔH⁺ was correlated to night temperature and PAR in A. nudicaulis. The proportion of ΔH⁺ derived from respiratory CO₂ also varied with experimental conditions. Thus percentage recycling was lower in A. fendleri under high PAR (0–10%), but was only reduced at 18 °C under low PAR. Recycling by A. nudicaulis ranged from 32–42% under high PAR, but was also reduced to 6% under low PAR at 18 °C; at 12 °C and 25 °C, recycling was 37% and 52% respectively. Previous studies have suggested a relationship between the proportion of recycling and degree of water stress. This study indicated that CAM as a CO₂ concentrating mechanism regulates both water-use efficiency and plant carbon balance in these epiphytes, in response to PAR and night temperature. However, the precise relationship between respiratory processes and the balance between external and internal sources of CO₂ is as yet unresolved.     

Measurement of immunoreactive cytochrome P450 2E1 in human leucocytes

We describe initial results on a Western blotting method, using a ployclonal antibody and chemiluminescence detection, for the measurement of cytochrome P450 2E1 in human lymphocytes. The method has been used to study the levels of 2E1 in lymphocytes isolated from 5 ml blood samples collected from a small group of well-controlled type 1 diabetics and healthy individuals. The described method offers increased sensitivity compared with a previously published method and does not need in vitro culturing of the lymphocytes prior to 2E1 measurement. The apparent molecular weight of the lymphocyte P450 2E1 was 55 kDa. There was approximately a six-fold difference in expression levels of 2E1 detected by this immunochemical technique across the study population.     

Aluminium Effects on ATPase Activity and Lipid Composition of Plasma Membranes in Sugar Beet Roots

The effect of aluminium (Al) in vivo and in vitro on root plasmamembranes has been studied in two sugar beet (Beta vulgarisL.) cultivars, Monohill (Al-sensitive) and Regina (relativelyAl-tolerant). Although Al in vitro inhibited the MgATPase inan uncompetitive way for both cultivars raised in the absenceof Al, the specific K⁺-activation of the MgATPase was only inhibitedby Al in cv. Monohill. Arrhenius analysis of the MgATPase activity showed that theeffect of Al in vitro depended on whether or not the plantswere exposed to Al in vivo. Al treatment in vitro of the MgATPasefrom control plants cultivated at a low pH (5·4) causedan increase in the phase transition temperature from 17 to 22°C. Only at a higher pH range (pH 6·1) could a secondtransition temperature be induced (at 9 °C). By additionof Al in vitro to plants cultivated with Al at pH 5·4,the slopes of the activity plots did not change. Aluminium changedthe K_m of the ATPase for MgATP in an opposite way by treatmentin vivo and in vitro. Lipid analyses of the plasma membranes showed that the acylcomposition differed little following Al treatment in vivo,but that the ratio of phosphatidylcholine: phosphatidylethanolamineincreased. The changes correlated with the observed change inthe K_m for the MgATPase. We conclude that the main effect ofAl on the MgATPase is not due to the formation of an Al-ATPcomplex. Instead, Al may bind to the membrane-bound enzyme(s)and/or modify the lipid environment. Key words: Aluminium, ATPase, Beta vulgaris, lipids     

You're so vein: bundle sheath physiology,phylogeny and evolution in C3 and C4 plants

Bundle sheath (BS) anatomy is found in most C4 lineages, associated with low inter‐veinal distances (IVD) and high BS:mesophyll ratio (BS:MC). The origins, function and selective advantages of the BS in C3 lineages are relevant for understanding the environmental, molecular and phylogenetic determinants of C4 evolution. Suggested functions for BS have included structural support, hydraulic isolation, storage for water, ions, and carbohydrates, and photorespiratory carbon metabolism; we propose a central role for cavitation repair, consistent with the BS as a control centre on regulating stem and leaf hydraulic continuity. An analysis of BS traits in the phylogenetic lineages giving rise to C4 grasses (the ‘PACMAD’ clade) shows an initial enhancement in BS:MC ratio in C3 lineages, although IVD is similar to the Pooideae sister group. Using a global database, a well‐developed BS in the C3 PACMAD lineages was associated with higher precipitation and temperatures in the habitat of origin on an annual basis, with the C3 to C4 progression defined by the aridity index (AI). Maintaining leaf hydraulic conductance and cavitation repair are consistent with increased evaporative demand and more seasonal precipitation as drivers, first for the C3 BS, and then C4 diversification, under declining CO₂ concentrations in the Palaeogene and Neogene.     

A review of the performance of electrostatically charged rotary atomisers on different crops

The collaborative trials described by Arnold et al., 1984a, b, c provided an extensive range of data on the performance of electrostatically charged rotary atomizers on a variety of crops, at different growth stages, using systemic and non-systemic pesticides. The purpose of this paper is to review the subject to date.     

Male-limited evolution suggests no extant intralocus sexual conflict over the sexually dimorphic cuticular hydrocarbons of <Emphasis Type="Italic">Drosophila melanogaster</Emphasis>

Sexually dimorphic traits are likely to have evolved through sexually antagonistic selection. However, recent empirical data suggest that intralocus sexual conflict often persists, even when traits have diverged between males and females. This implies that evolved dimorphism is often incomplete in resolving intralocus conflict, providing a mechanism for the maintenance of genetic variance in fitness-related traits. We used experimental evolution in Drosophila melanogaster to directly test for ongoing conflict over a suite of sexually dimorphic cuticular hydrocarbons (CHCs) that are likely targets of sex-specific selection. Using a set of experimental populations in which the transmission of genetic material had been restricted to males for 82 generations, we show that CHCs did not evolve, providing experimental evidence for the absence of current intralocus sexual conflict over these traits. The absence of ongoing conflict could indicate that CHCs have never been the target of sexually antagonistic selection, although this would require the existing dimorphism to have evolved via completely sexlinked mutations or as a result of former, but now absent, pleiotropic effects of the underlying loci on another trait under sexually antagonistic selection. An alternative interpretation, and which we believe to be more likely, is that the extensive CHC sexual dimorphism is the result of past intralocus sexual conflict that has been fully resolved, implying that these traits have evolved genetic independence between the sexes and that genetic variation in them is therefore maintained by alternative mechanisms. This latter interpretation is consistent with the known roles of CHCs in sexual communication in this species and with previous studies suggesting the genetic independence of CHCs between males and females. Nevertheless, direct estimates of sexually antagonistic selection will be important to fully resolve these alternatives.