Aerobic heat shock activates trehalose synthesis in embryos of Artemia franciscana.

Encysted embryos (cysts) of the brine shrimp, Artemia franciscana, contain large amounts of trehalose which they use as a major substrate for energy metabolism and biosynthesis for development under aerobic conditions at 25 degrees C. When cysts are placed at 42 degrees C (heat shock) these pathways stop, and the cysts re-synthesize the trehalose that was utilized during the previous incubation at 25 degrees C. Glycogen and glycerol, produced from trehalose at 25 degrees C, appear to be substrates for trehalose synthesis during heat shock. Anoxia prevents trehalose synthesis in cysts undergoing heat shock. These results are consistent with the view that trehalose may play a protective role in cells exposed to heat shock, and other environmental insults, in addition to being a storage form of energy and organic carbon for development.     

Photoproduction of hydrogen, nitrogenase and hydrogenase activities of free and immobilized whole cells of Rhodobacter sphaeroides O.U. 001

Abstract Photoproduction of hydrogen, nitrogenase activity (acetylene reduction) and hydrogenase activity (methylene blue dye reduction) were studied in free and alginate immobilized whole cells of a purple non-sulfur photosynthetic bacterium Rhodobacter sphaeroides O.U. 001. Four-fold increase in hydrogen production, two-fold increase in nitrogenase activity and 1.2-fold increase in the hydrogenase activity were observed in immobilized cells compared to free cells. Effect of various inhibitors (CO and C₂H₂) and electron donor (H₂) on the above three functions by free and immobilized cells has also been studied.     

Glucocorticoid receptor binding to calf thymus DNA. 1. Identification and characterization of a macromolecular factor involved in receptor-steroid complex binding to DNA.

Activation of receptor-steroid complexes to a form with high affinity for DNA is a poorly understood process involving multiple components in addition to the holoreceptor. Employing rat HTC cells as the source of glucocorticoid receptor, we show that maximal receptor binding to calf thymus DNA is mediated by a previously unknown small molecular weight factor. This factor can be removed from cytosolic preparations of receptor by gel filtration chromatography. Salt extraction of crude nuclear pellets afforded much larger amounts of a similar DNA-binding activity factor. The cytoplasmic factor and the more abundant nuclear factor were identical on the basis of their similar physical properties. The factor was precipitable in the crude state with (NH4)2SO4 and stable to heat as well as freezing and thawing. Chromatography on DNA-cellulose revealed that the factor itself did not bind to DNA. The factor could be filtered through a Centricon C-3 microconcentrator (molecular weight cutoff approximately 3000) but was excluded from Sephadex G-10 columns. These parameters enable us to determine an apparent molecular weight of 700-3000 for this factor. The presence of large amounts of this factor in nuclei accounts for the previously unexplained observation that, following size exclusion chromatography, more activated complexes bind to nuclei than to DNA. These data indicate that some, but not all, of the activated complexes require factor to be able to bind to DNA. The predominantly nuclear localization of this factor, coupled with its ability to increase DNA binding, attests to the biological relevance of this factor in the whole cell action of receptor-glucocorticoid complexes.     

Transmission of parasites in the coastal waters of the Arctic seas and possible effect of climate change

The review deals with the biodiversity, life cycles, distribution and temperature adaptations of parasites circulating in the coastal waters of northern polar seas. Special attention is given to helminths of marine birds, which are the most common parasites in the coastal waters. Among them, the focus is on trematodes. Factors responsible for the impoverished species composition of parasites in the Arctic are analyzed. It is shown that species without free-living larvae in the life cycle have an advantage in this environment. The abundance of cestodes and acanthocephalans in Arctic seabirds is linked with the high proportion of crustaceans in their diet. The phenomenon of nonspecific parasitism (occurrence of parasites in atypical host species) is analyzed from an evolutionary viewpoint. Characteristic features in the spatial distribution of infection of marine coastal invertebrates with parasite larvae are considered, and factors that determine it are specified. The prevalence of infection in intermediate hosts is closely connected with the abundance of final hosts, which makes it possible to estimate the abundance of final hosts in a given region and reveal trends in its changes. Trematodes have a high potential for temperature acclimation. This facilitates their transmission in the northern seas but, on the other hand, makes it unlikely that the transmission process would be intensified upon an increase in summer temperatures resulting from climate warming. However, intensification of transmission may well occur due to the prolongation of the warm season (“transmission window”), which has been predicted and is already observed. It is suggested that warming in the Arctic promotes both the entry of certain “southern” species into the Arctic and the trans-Arctic interpenetration of the North Atlantic and North Pacific parasitic faunas. A case is made for the necessity to broaden the scope of parasitological research in the Arctic and Subarctic, including parasitological monitoring at the reference sites of the sea coast.     

Functional role of phenylacetic acid from metapleural gland secretions in controlling fungal pathogens in evolutionarily derived leaf-cutting ants

Fungus-farming ant colonies vary four to five orders of magnitude in size. They employ compounds from actinomycete bacteria and exocrine glands as antimicrobial agents. Atta colonies have millions of ants and are particularly relevant for understanding hygienic strategies as they have abandoned their ancestors'' prime dependence on antibiotic-based biological control in favour of using metapleural gland (MG) chemical secretions. Atta MGs are unique in synthesizing large quantities of phenylacetic acid (PAA), a known but little investigated antimicrobial agent. We show that particularly the smallest workers greatly reduce germination rates of Escovopsis and Metarhizium spores after actively applying PAA to experimental infection targets in garden fragments and transferring the spores to the ants'' infrabuccal cavities. In vitro assays further indicated that Escovopsis strains isolated from evolutionarily derived leaf-cutting ants are less sensitive to PAA than strains from phylogenetically more basal fungus-farming ants, consistent with the dynamics of an evolutionary arms race between virulence and control for Escovopsis, but not Metarhizium. Atta ants form larger colonies with more extreme caste differentiation relative to other attines, in societies characterized by an almost complete absence of reproductive conflicts. We hypothesize that these changes are associated with unique evolutionary innovations in chemical pest management that appear robust against selection pressure for resistance by specialized mycopathogens.     

Morphometric parameters of neurons in reticular nuclei of the brain stem in kittens

Three types of Golgi-stained neurons were discovered in brain stem reticular nuclei of 30-day-old kittens: sparsely branching reticular neurons, those with densely branching dendritic trees, and giant multipolar neurons (Leontovich's classification). Adopting computerized morphometric techniques enabled 23 different parameters to be measured in cells of these types. The measurements taken from the neuronal groups investigated revealed statistically significant differences between them for most parameters. It was concluded from this that each of the neuronal types distinguished has its own morphological identity (or stability). Characteristics of structural differences and properties of differing cell types in reticular nuclei are discussed in relation to their functional properties.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 23, No. 4, pp. 399–409, July–August, 1991.     

Possible explanation of the disparity between the in vitro and in vivo measurements of Rubisco activity: a study in loblolly pine grown in elevated pCO2.

Rubisco activity can be measured using gas exchange (in vivo) or using in vitro methods. Commonly in vitro methods yield activities that are less than those obtained in vivo. Rubisco activity was measured both in vivo and in vitro using a spectrophotometric technique in mature Pinus taeda L. (loblolly pine) trees grown using free-air CO2 enrichment in elevated (56 Pa) and current (36 Pa) pCO2. In addition, for studies where both in vivo and in vitro values of Rubisco activity were reported net CO2 uptake rate (A) was modelled based on the in vivo and in vitro values of Rubisco activity reported in the literature. Both the modelling exercise and the experimental data showed that the in vitro values of Rubisco activity were insufficient to account for the observed values of A. A trichloroacetic acid (TCA) precipitation of the protein from samples taken in parallel with those used for activity analysis was co-electrophoresed with the extract used for determining in vitro Rubisco activity. There was significantly more Rubisco present in the TCA precipitated samples, suggesting that the underestimation of Rubisco activity in vitro was attributable to an insufficient extraction of Rubisco protein prior to activity analysis. Correction of in vitro values to account for the under-represented Rubisco yielded mechanistically valid values for Rubisco activity. However, despite the low absolute values for Rubisco activity determined in vitro, the trends reported with CO2 treatment concurred with, and were of equal magnitude to, those observed in Rubisco activity measured in vivo.     

A preliminary analysis of distribution patterns in a large, pantropical genus, Barleria L. (Acanthaceae)

Barleria L. (Acanthaceae) is a large, polymorphic, widespread genus of herbs and shrubs comprising about 300 species, occurring mainly in Africa and Asia but with one species, Barleria oenotheroides Dum.Cours., extending to the New World tropics. Recent completion of a monographic infra-generic classification of the genus (in which seven sections are recognised, and the names of four of these validated in this paper—see Appendix 1), has facilitated a comprehensive analysis of distribution patterns on a global scale. The richest representation of Barleria is in Africa where there are two centres of diversity, one in tropical East Africa (about eighty species) and the other in southern Africa (about seventy species). The number of species tails off rapidly to both the Far East and the West. Barleria shows a marked trans-Atlantic disjunction between West Africa and the Neotropics, with B. oenotheroides shared by these two regions. This type of disjunction, which is known in other genera of the family, cannot be adequately explained in Barleria on the basis of long-distance dispersal or past continental movements. There is a high degree of regional endemism (e.g. 75% for the Indian subcontinent) at both the species and sectional levels within this genus. The degree of similarity between regions is correspondingly low. The endemics in each region tend to belong to only one or a few of the sections. There are few truly widespread taxa within the genus. East and West Africa are the only regions in which all sections are represented. Sections Barleria and Prionitis C.B. Cl. are the most widespread in the genus; Sections Somalia (Oliv.) Lindau, Fissimura M. Balkwill and Stellatohirtae M. Balkwill are mainly restricted to Africa and Sections Chrysothrix M. Balkwill and Cavirostrata M. Balkwill are the most restricted, occurring mainly in India and Sri Lanka. On a local scale, many of the species show highly restricted, clumped distributions; this is apparently related to particular soil types and possibly to the short-distance, ballistic mode of seed dispersal. This account of the biogeography of Barleria is to be regarded as preliminary, as much taxonomic work at the species level remains to be done before a full-scale cladistic biogeographic account can be undertaken. Particular areas worthy of future investigation include establishing the centre of origin of the genus and investigating the basis for the high degree of endemism shown by many of the species.