Contractility of Glycerinated Amoeba proteus and Chaos-chaos*

Immediate contact with large volumes of cold 50% (v/v) buffered glycerol preserved typical ameboid shape of Chaos chaos and Amoeba proteus with no visible distortions. These technics allowed determination of the contraction sites in these glycerinated models upon application of ATP-Ca-Mg-solutions. The ectoplasmic tube was the main site of contraction. Preliminary EM investigations revealed thick and thin filaments, associated with the ectoplasmic tube near the plasmalemma, which appeared to be the basis for the contractility of the ectoplasmic tube. There was no predominant contraction of the pseudopodial tips or the endoplasm in these models. The changes of volume were as much as 50%, and in some cases were not accompanied by any change in the length of the ameba; however, lengthwise contractions of the ectoplasmic tube in some amebae occurred to as much as 25%. The data substantiate a basic requirement of the ectoplasmic tube contraction theory of ameboid locomotion.     

INTERACTIONS OF 1-METHYLADENINE AND THE SURFACE OF STARFISH OOCYTE

Three metabolic inhibitors, mycostatin, concanavalin A (Con A) and cytochalasin B (CB) were used to study the interactions between l-methyladenine (1-MA) and the starfish oocyte surface leading to germinal vesicle breakdown (GVB). Mycostatin and Con A had no obvious effects on GVB. CB did not inhibit, but did delay GVB. This delaying effect was interpreted as having multiple 1-MA reactive "sites" on the surface. The results also suggested that not all of them were needed to react with 1-MA to bring about GVB.     

Prey caught by a sample population of the spider Argiope argentata (Araneae:Araneidae) in Panama:a year's census data

The prey caught by mature female Argiope argentata was censused over a period of one year. Ten webs (when available) were examined five times each day, at two-hourly intervals, between 09.00 and 17.00 hours. The prey-animals seen in the webs were classified into orders and lower taxa, where possible. The results of this study are described and discussed.     

Evaluation of some coccinellid species for the biological control of aphids in protected cropping

Four species of Coccinellidae, Adalia bipunctata (L.), Coccinella septem-punctata L., Coelomegilla maculata de G. and Cycloneda sanguinea L., were compared as predators of aphids on cucumbers and chrysanthemums. In laboratory feeding tests C. maculata and C. sanguinea proved the most voracious but the former could not remain on cucumber foliage long enough to be effective. The fecundity of C. sanguinea was the highest of those studied and a satisfactory laboratory rearing technique has been developed for this species.     

The fusicoccin-stimulated phosphorylation of a 33 KDa polypeptide in cells of Acer pseudoplatanus as influenced by extracellular and intracellular pH

Abstract In a previous study, it was shown that the fungal toxin fusicoccin (FC) is able to stimulate the in vivo phosphorylation of a 33 KDalton polypeptide (33 KP) independently of protein synthesis. Here we show that the stimulation by FC of both proton efflux and 33 KP phosphorylation are strongly enhanced when the external medium contains K⁺ or Na⁺, suggesting that the two phenomena are related. The stimulatory effect of FC is higher in unbuffered than in buffered media; moreover, in the absence of FC, 33 KP is more phosphorylated at an acidic than at a basic pH of the medium, suggesting that the effect of FC may depend, to a certain extent, on the acidification of the free space caused by FC-promoted proton efflux. Treatments reported to alter the intracellular pH influence 33 KP phosphorylation even more strongly than the external pH does. The acidifying agents isobutyric acid and trimethylacetic acid decrease 33 KP phosphorylation, while the alkalinizing agents, ammonia and procaine, increase it. FC partially counteracts the inhibition by the weak acids, whereas the stimulatory effect of FC is not additive with that of the weak bases. The results indicate that 33 KP phosphorylation senses both the external and internal pH. The stimulatory effect of cytoplasm-alkalinizing treatments, which mimics that of FC, agrees with the reported capacity of FC to cause cytoplasmic alkalinization, following activation of the plasmalemma proton pump.     

IMPORTANCE OF REFERENCE STANDARDS IN TRAINING PANELISTS

When training a sensory evaluation panel, reference standards play an important role in developing appropriate terminology, establishing intensity ranges and showing the action of an ingredient. In addition, use of reference standards reduces the amount of training time while providing documentation for terminology. Product characteristics can be demonstrated through reference standards for application in plant quality assurance programs as well as for project planning in new product development, product maintenance (i.e., shelf-life), product improvement and cost reduction programs.     

Polyamines, storage substances and abscisic acid-like inhibitors during dormancy and very early activation of Helianthus tuberosus tuber tissues

Abstract Dormancy and break of dormancy of tubers of Helianthus tuberosus L. (Jerusalem artichoke) have been investigated in regard to the possibility that polyamines can control these processes. Polyamines were detected by the method of direct dansylation and abscisic acid was bioassayed using wheat coleoptile growth test. Arginine and glutamine, which are the main store nitrogenous organic compounds of Helianthus tuberosus tuber, decrease during the last phase of dormancy as well as abscisic acid; moreover the corresponding increase in polyamines (putrescine, spermidine and spermine) seems to be strictly related to the break of dormancy of tuber. The artificial break of dormancy induced by 2,4-dichlorophenoxyacetic acid stimulates a great increase in polyamines, just evident within 15 min after activation, and a corresponding decrease in arginine and glutamine. The levels of polyamines, at 1 h of activation are sufficient to stimulate protein synthesis in vitro.     

An Electronmicroscopic Study of the Microgamete of Haemoproteus columbae Kruse*

SYNOPSIS. Microgametes of Haemoproteus columbae were studied by light microscopy and electron microscopy, using the single-stage replication technic. The filiform microgamete has a swelling or vesicle near the round end; the opposite end is asymmetrically tapered. The gamete is polarized, for it travels in sinuous movements with the round end (the putative anterior end) directed forward. There is no flagellum or undulating membrane and no mitochondrion. The vesicle may contain energy reserves for locomotion or lytic enzymes for penetration. Tubular material often is seen coming from the vesicle and anterior end and may be a kind of acrosomal filament.     

Distinction between Two Types of Beta-Thalassaemia by Inducibility of the Cell-free Synthesis of Beta-Chains by Nonthalassaemic Soluble Fraction

β-THALASSAEMIA is a hereditary anaemia in which the β-chains of haemoglobin, though structurally normal, are synthesized abnormally slowly. The β-thalassaemia of the Ferrara region of Italy is distinguished in the homozygote by β-chain synthesis which is not merely reduced but completely absent. It has recently been reported that, in a cell-free system, ribosomes from such subjects do not make β-chains in the presence of their own supernatant but do when nonthalassaemic supernatant is substituted¹. It was shown that this effect was due to a factor other than mRNA.