Physiological changes accompanying the recovery of cell division in "giant" cells of Chlorella vulgaris (EMERSON strain)

A homogeneous population of "giant" cells of the EMERSON strainof Chlorella vulgaris, produced following culture under carefullycontrolled conditions in a glucose medium in the dark, recoversits capacity to undergo cell division when returned to autotrophicconditions. A similar recovery also occurs after a prolongedperiod of culture in the dark. The division of the giant cellsis accompanied, in each case, by marked pigment synthesis anda consequent recovery of photosynthetic capacity. Under autotrophicconditions the recovery of cell division and restoration ofthe full pigment concentration are complete within a 24 hr period.The recovery which takes place in a glucose medium in the darkoccurs only after a period of 10–14 days growth. (Received May 9, 1970; )     

PRIMARY PEPTIDE SEQUENCES FROM SQUID MUSCLE AND OPTIC LOBE MYOSIN IIs: A STRATEGY TO IDENTIFY AN ORGANELLE MYOSIN

The squid giant axon provides an excellent model system for the study of actin-based organelle transport likely to be mediated by myosins, but the identification of these motors has proven to be difficult. Here the authors purified and obtained primary peptide sequence of squid muscle myosin as a first step in a strategy designed to identify myosins in the squid nervous system. Limited digestion yielded fourteen peptides derived from the muscle myosin which possess high amino acid sequence identities to myosin II from scallop (60–95%) and chick pectoralis muscle (31–83%). Antibodies generated to this purified muscle myosin were used to isolate a potential myosin from squid optic lobe which yielded 11 peptide fragments. Sequences from six of these fragments identified this protein as a myosin II. The other five sequences matched myosin II (50–60%, identities), and some also matched unconventional myosins (33–50%). A single band that has a molecular weight similar to the myosin purified from optic lobe copurifies with axoplasmic organelles, and, like the optic lobe myosin, this band is also recognized by the antibodies raised against squid muscle myosin II. Hence, this strategy provides an approach to the identification of a myosin associated with motile axoplasmic organelles.     

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.     

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.     

SOME PHYSIGOCHEMICAL ASPECTS OF THE MACROAND MICROENVIRONMENTS SURROUNDING HYDRA DURING ACTIVATION OF THEIR FEEDING BEHAVIOR

Three environmental zones which can influence the activationof the feeding response of Hydra littoralis are termed the macro-,micro-, and ultramicroenvironment. The first consists primarilyof the ions in the bulk medium, and of dissolved gases. Themicroenvironment is the area immediately surrounding the hydra;its composition is influenced by substances emitted from andtaken up by the animal. The third zone, the ultramicroenvironment,is presumed to be made up of a thin shell of ions in the mediumthat are attracted to the charged surfaces of the animal. Through a physicochemical study of these environments, we havedetermined: (1) the presence of ionizable groups at the receptorsite which may be involved in the binding of glutathione; (2)the role of potassium and other ions in influencing the feedingresponse; and, (3) the possible existence of charged surfaceson hydra surrounded by a pH shell. Further, these experimentshelp to resolve many seemingly inconsistent reports dealingwith the feeding behavior of hydras.     

Crops that stay green1

Genetic variation exists for foliar senescence and has, usually incidentally or empirically, been exploited for crop improvement. We review the incidence of delayed or inoperative senescence in maize, sorghum, oats, rice, wheat, fescue, soybean, french bean, fruit crops, trees and other species. The insights such variants give into the genetic control of leaf senescence, and the practical implications of improved understanding of the stay-green phenomenon are discussed.