Effect of Sodium on Phosphate Uptake in Unicellular and Filamentous Cyanobacteria

The effect of Na⁺ on phosphate uptake was studied in four strainsof cyanobacteria: Synechococcus PCC 7942, Gloeothece PCC 6501,Phormidium sp. and Chlorogloeopsis PCC 6912. Phosphate uptakewas stimulated by Na⁺ in all cases. Li⁺ and K⁺ acted as partialanalogues for Na⁺. Half-saturation [K_1/2(Na⁺)] of phosphateuptake was reached with Na⁺ concentrations ranging from 317µM in Chlorogloeopsis to 659 µM in Phormidium. Theconcentration of phosphate required to reach half-saturationof phosphate uptake [K_1/2(P_i)]was not changed by the presenceof Na⁺. (Received April 11, 1994; Accepted July 5, 1994)     

Trinucleotide (CAG) repeat expansion in chromosomes of Spanish patients with Huntington's disease

Huntington's disease (HD) is a neurodegenerative and hereditary disease characterized by progressive movement disorders and mental and behavioral abnormalities. The HD gene is an expanding and unstable trinucleotide repeat (CAG repeat sequences). We studied 77 individuals from 38 families with HD in an attempt to obtain information for genetic counselling and differential diagnosis. Our results indicate that individuals with more than 40 repeats will be affected by the disease, whereas those with fewer than 30 will be healthy. There can be some overlap between 30 and 40 repeats, and one should be careful when interpreting these results.     

Plankton distribution across a slope current-induced front in the southern Bay of Biscay

Relatively warm (12.50–12.75°C) and high-salinity[<35.640 practical salinity units (PSU)] water flowing eastwardwas detected at the shelf-break during a cruise carried Outin the southern Bay of Biscay in Spring 1987. The slope currentinduced the formation of a convergent front separating well-mixedoceanic waters from haline-stratified coastal waters. Very highconcentrations of dissolved oxygen (295 µmol kg^–1)and chlorophyll a(>4.5 mg m^–3) were found at the outeredge of the frontal boundary. Small autotrophic flagellatesdominated the phytoplankton community. Primary production peakedat the boundary region. Estimated phytoplankton growth ratesindicated that active growth was taking place, with lower turnovertimes integrated over the water column at the frontal station(2.5–5 days) than at coastal (1.5–2.8 days) or oceanic(1.5–3.5 days) stations. The lowest doubling times (1–2days) were calculated for surface frontal populations. Accumulationof zooplankton was also observed associated with the convergentphysical structure, although this relationship was less markedthan for phytoplankton. Copepods, mainly Paracalanus parvus,Acartia clausi and Oithona helgolandica, formed the bulk ofthe mesozooplankton biomass. Compatibility between the sizeof phytoplankton cells and copepod size spectra indicate highfood availability for these animals, particularly in the vicinityof the front. The distribution of fish eggs and fish larvaewas also coupled with the slope current-induced front. Sardinelarvae were more abundant at the coastal side of the front,whereas larval stages of blue whiting reached the highest densitiesat off-shelf stations. Larvae of lamellibranch molluscs andbryozoa were restricted to nearshore waters, as the frontalboundary prevented larval dispersion to the open ocean. Theresults presented in this paper suggest that the Iberian slopecurrent and its associated shelf-break frontal structure werecrucial in controlling phytoplankton primary production, activityof grazers, distribution of larvae of fishes and benthic invertebrates,and ultimately in determining the structure of the pelagic foodweb in the southern Bay of Biscay during the seasonal periodof vertical mixing.     

Enumeration of Obesumbacterium proteus in brewery yeasts and characterization of isolated strains using Biolog GN microplates and protein fingerprinting

Of a range of media tested for enumeration of Obesumbacterium proteus in brewers' yeast, Universal Beer agar and Wallerstein Laboratories Differential medium were most effective. MacConkey agar (several types) and Membrane Lauryl Sulphate agar were least effective. Other media (Wort agar, YM agar) were of intermediate efficacy. Nine O. proteus strains from commercial yeast samples were characterized using the API 20E test kit, the Biolog GN microplate (BGNM) and by SDS-PAGE of their total soluble proteins. Both the BGNM and SDS-PAGE techniques allowed the strains to be differentiated from one another: the API 20E kit did not. All strains isolated from UK breweries belonged to O. proteus biogroup II. Four of these strains displayed a branching cell morphology not hitherto described in any member of the Enterobacteriaceae.     

Use of Synthetic Peptides to Study the Function of GTPases Regulating Vesicular Traffic

We describe the application of synthetic peptides to explore the function of GTPases regulating vesicular traffic through the constitutive and regulated exocytic pathways. The utility of the approach is discussed in the context of the parameters that limit or enhance the effectiveness of these reagents in eliciting a biologically relevant response.     

Combined effect of ambient temperature and solar radiation on maned sloths' behaviour and detectability

Changes in ambient temperature and solar radiation may affect sloths' metabolic rate and body temperature, with consequent changes in activities, postures and microhabitat selection. Although the separate effect of temperature and solar radiation on sloth's behaviour have been previously studied, the combined effect of these climatic factors on behavioural aspects of sloths has never been systematically evaluated in field conditions. Here we evaluated the influence of hourly ambient temperature variation on maned sloth (Bradypus torquatus) activities, postures and tree crown positions, under sunny and cloudy conditions; and tested if any of the animal posture and position increase their exposure to human detection. We performed 350 h of visual observation on eight maned sloths, equipped with radio-backpacks, in northern Bahia, Brazil, recording their activities, and their resting postures and positions on tree crowns. We also recorded the time taken to visualize the sloths on 58 days to analyse if sloths' detection is affected by posture and position. Higher ambient temperature, within a range of 21–33°C, increased the sloths' activity levels in cloudy conditions but reduced their activity in sunny conditions. Increasing ambient temperature also reduced the frequency of huddled posture and increased the frequency of extended posture and permanence in the inner tree crown. Lastly, the postures and positions did not influence sloths' detectability. Thus, the direction of the temperature–activity relationship depends on climatic conditions (sunny/cloudy), and individuals rely on resting postures and positions to thermoregulate. The warmer and drier future climate, expected to occur in the northern Atlantic Forest, may impose change in the diurnal activity levels and postural pattern for this threatened species, leading maned sloths to reduce its activity on sunny and warmer days and adopting an extended posture.     

Hepatic changes during a carrageenan induced granuloma in rats

Hepatic changes during inflammation were studied in rats bearing a carrageenan induced granuloma. In spite of a decrease in the metabolic capacity of microsomes to induce lipid peroxidation during inflammation, the endogenous lipid peroxidation remained unchanged and unrelated with the hepatic activities measured. The continuous increase in hepatic cAMP observed during acute and chronic phases could be related to adenylate cyclase stimulation by mediators, and could be an initial step in the hepatocyte adaptation leading to the increased level of hepatic caeruloplasmin, to the reduction of cytochrome P-450 level and to the modifications of Ca(2+) sequestration by microsomes.     

Changes in phytoplankton ecophysiology across a coastal upwelling front

The abundance, taxonomic composition and patterns of macromolecularsynthesis of phytoplankton were determined across an upwelling-inducedthermal front in the central Cantabrian Sea (southern Bay ofBiscay) during July 1993. Enhanced levels of phytoplankton biomass,diatom abundance and photosynthetic rate were measured on thecoastal side of the front. Relative carbon (C) incorporationinto proteins increased noticeably on the oceanic side, takingvalues of up to 64%, whereas changes in the relative C incorporationinto lipids and low-molecular-weight metabolites followed anopposite trend. Phytoplankton cells on the oceanic side of thefront were adapted to the prevailing growth-limiting conditionsby maintaining the synthesis of functionally essential molecules—proteins—ratherthan the synthesis of storage compounds. As a result, the carbonto nitrogen uptake ratio varied from {small tilde}5.7 in offshorewaters to 8.0 in the nearshore region. Our results suggest thatthe taxonomic and physiological changes in phytoplankton assemblagesas a response to upwelling may result in an increase in thesynthesis of organic C relative to the upward flux of nitrate.