Microbiological Synthesis of Fat: THE EFFECTS OF NITROGEN LEVEL ON THE METABOLISM OF PENICILLIUM LILACINUM THOM IN A SUCROSE MEDIUM

1. A study has been made of the relationships between the synthesesof carbohydrate, protein, and fat by Penicillium lilacinum Thomin presence of different amounts of sodium nitrate us a definedsucrose salts medium.
2. Under the defined experimental conditionsincreases in the concentrationof NO^–₂ in the medium werefollowed by increases in therates at which nitrogen and sugarwere taken up by the fungus,in the quantities assimilated,and in total and protein nitrogenin the felt. These conditionsprevailed so long as unassimilatedsugar was available.
3. Mediaof lower NO^–₃ concentration (for example, 0·32or 0·64 per cent. (w/v) NaNO^–₂;) yielded feltsricher in carbohydrate than were those grown in media of higherNO^–₂; content (0·96 or 1·28 per cent. (w/v)NaNO₃ The carbohydrate content of the felts increased graduallyuntil the sugar in the medium was exhausted; carbohydrate contentthen decreased.
4. Media of lower NO^–₃; concentration weremore conduciveto fat synthesis than those of higher NO^–₃;content.

     

Differential Stimulation of PEP-carboxylation in Guard Cells and Mesophyll Cells by Ammonium or Fusicoccin

Dark CO₂-fixation in guard cells of Vicia faba was much moresensitive to ammonium than in mesophyll cells. Addition of ammonium(5.0 mol m^–3; pH₀ 7.6) caused up to a 7-fold increasein dark CO₂-fixation rates in guard cell protoplasts (GCP),whereas in leaf slices, mesophyll cells, and mesophyll protoplaststhe increase was only about 1.4-fold. In both cell or tissuetypes, total CO₂-fixation rates were higher in the light (2–12-foldhigher in GCP and 28-fold in mesophyll); these rates were onlyslightly changed by ammonium treatment. However, separationof ¹⁴C-labelled products after fixation of CO₂ in the lightby GCP revealed a large ammonium-induced shift in carbon flowfrom starch and sugars to typical products of C₄-metabolism(mainly malate and aspartate). In contrast, in mesophyll cellsamino acid and malate labelling was only moderately increasedby ammonium at the expense of sucrose. The data suggest thatin vivo ammonium might facilitate stomatal opening and/or delaystomatal closing through an increased production of organicacids. Key words: PEP-carboxylation, guard cell protoplasts, ammonium, fusicoccin     

The Contribution of TRPV4-Mediated Calcium Signaling to Calcium Homeostasis in Endothelial Cells

A large variety of cation transport systems are involved in the regulation of calcium homeostasis in endothelial cells. The focus of the present study is to determine the contribution of nonselective cation channels from the TRP (transient receptor potential) family to cellular calcium homeostasis of porcine aortic endothelial cells (PAEC). One member of the TRPV (vanniloid) subfamily, TRPV4, has previously been shown to be involved in cation transport induced by a large variety of stimulations including osmolarity, temperature, mechanical stress, and phosphorylation. Here, we demonstrate the existence of several TRP proteins, including TRPV4, in PAEC using RT-PCR. To test whether this channel is functional, we performed FURA-2 calcium measurements and whole-cell patch-clamp experiments. We observed the induction of large calcium signals following mechanical stress, altered extracellular temperature, and the selective TRPV4 activator 4-α -PDD. These effects were diminished in the presence of the TRPV4 inhibitor miconazole, suggesting the involvement of this channel in mediating endothelial calcium signals. The large amounts of transported calcium and the short signaling ways suggest a potentially important role of this channel in many physiological processes.     

The Diving Response Mechanism and its Surprising Evolutionary Path in Seals andSea Lions

During the last half century or more, studies of diving physiologyand biochemistry made great progress in mechanistically explainingthe basic diving response of aquatic mammals and birds. Keycomponents of the diving response (apnea, bradycardia, peripheralvasoconstriction, redistribution of cardiac output) were foundin essentially all species analyzed and were generally takento be biological adaptations. By the mid 1970s, this approachto unravelling the diving response had run 'out of steam' andwas in conceptual stasis. The breakthrough which gave renewalto the field at this time was the development of microprocessorbased monitoring of diving animals in their natural environments,which led to a flurry of studies mostly confirming the basicoutlines of the diving response based upon laboratory studiesand firmly placing it into proper biological context, underliningits plasticity and species specificities. Now towards the endof the millenium, despite ever more detailed field monitoringof physiology, behaviour and ecology, mechanistic studies areagain approaching a point of diminishing returns. To avoid anotherconceptual stasis, what seems required are new initiatives whichwe anticipate may arise from two differing approaches. The firstis purely experimental, relying on magnetic resonance imaging(MRI) and spectroscopy (MRS) to expand the framework of theoriginal "diving response" concept. The second—evolutionarystudy of the diving response—is synthetic, linked to bothfield and laboratory studies. To date the evolution of the divingresponse has only been analyzed in pinnipeds and from thesestudies two kinds of patterns have emerged. (1) Some physiologicaland biochemical characters, required and used in diving animals,are highly conserved not only in pinnipeds but in all vertebrates;these traits are necessarily similar in all pinnipeds and includediving apnea, bradycardia, tissue specific hypoperfusion, andhypometabolism of hypoperfused tissues. (2) Another group offunctionally linked characters are more malleable and include(i) spleen mass, (ii) blood volume, and (iii) hemoglobin (Hb)pool size. Increases in any of these traits improve diving capacity.Assuming that conserved physiological function means conservedsequences in specific genes and their products (and that evolvingfunction requires changes in such sequences), it is possibleto rationalize both above trait categories in pinniped phytogeny.However, it is more difficult for molecular evolution theoryto explain how complex regulatory systems like those involvedin bradycardia and peripheral vasoconstriction remain the samethrough phylogenetic time than it is to explain physiologicalchange driven by positive natural selection.     

Genetic diversity in Atlantic Forest trees: fragmentation effects on Astronium graveolens (Anacardiaceae) and Metrodorea nigra (Rutaceae), species with distinct seed dispersal strategies

We explore the genetic structure and variability in autochorous Metrodorea nigra (Rutaceae) and anemochorous Astronium graveolens (Anacardiaceae), two species affected by deforestation in the Atlantic Forest of Brazil. The effects of deforestation and the depletion of the habitat within the remaining patches of forest are evaluated by comparing the variability between saplings and adults of each of these two species. The results indicate that the depletion of forest land and the deteriorating condition of the remaining fragments of forest may reduce the level of endogamous breeding in wind‐dispersed species. In autochorous species, the fragmentation of forest land has less notable effects on genetic attributes, but pollen flow could be decreased as a result of the reduced number of insects flying between the forest remnants. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 164 , 326–336.     

Collective Action and Social Capital of Wildlife Management Associations

Abstract: In areas with dense landownership patterns, management of white-tailed deer (Odocoileus virginianus) depends upon collective decision making of landowners and hunters. To resolve conflicts associated with this commons dilemma, wildlife management associations (WMAs) have become a popular mechanism for coordinating wildlife management decisions in private land states, especially in Texas, USA. Social capital, represented by metrics such as trust, reciprocity, and community involvement, has been identified as an important determinant of the success of collaborative institutional arrangements. To determine the influence of social capital on the effectiveness of WMAs, we address 2 research questions: 1) do WMAs exhibit elements of social capital, and 2) what landowner characteristics affect elements of social capital within WMAs? We used a mail survey questionnaire to determine the effect of various factors on the activities and management practices in 4 WMAs in 2 regions in Texas: the Lower Post Oak Savannah (LPOS) and the Central Post Oak Savannah (CPOS). The LPOS landowners were members of larger associations, had generally acquired their land more recently, held more frequent meetings, and tended to have longer association membership than CPOS landowners, yet they exhibited lower social capital. The CPOS landowners owned significantly larger properties, and were predominantly absentee wealthy males that considered relaxation and hunting more important land uses than property ownership for a place to live. The smaller group size of the CPOS associations may be the most important factor in building and maintaining social capital. Intra-association trust, a primary measure of social capital, was positively influenced by the longevity of property ownership, the number of association meetings, the percentage of males in the association, and other factors. Conversely, negative influences on trust included absentee ownership and the proportion of woodland habitat present in each WMA. We suggest that deer are a common-pool resource whose populations are dependent upon collective action by stakeholders. Social capital building within landowner associations could facilitate the sustainable harvest of quality deer and possibly lead to cooperative management of other common-pool natural resources.     

Ammonium and phosphate regenerationby the zooplankton of an Amazon floodplain lake

SUMMARY. 1. Regeneration of ammonium and phosphate by macro-zooplankton (Cladocera. adult copepods. and copepodites) was measured in Lake Calado. an Amazon floodplain lake, Macrozooplanktonabundances ranged between 1×10⁴ and 3×10⁵ individuals m⁻².
2. Phosphate regeneration ranged from 0.2 to 1.3 μ mol PO₄ m⁻² b⁻¹at station 1. located 2 km from the Solimoes River, and from 1.6 to8.3 μ mol PO₄ m⁻² h ⁻¹ at station 3, located 7 km from the SolimoesRiver. Ammonium regeneration at stations 1 and 3 ranged from 1.7 to11.9 and from 13.4 to 77.2 μ mol NH₄ m⁻² h⁻¹. respectively.
3. Zooplankton regenerated ammonium and phosphate at similarrates during rising and falling waier. Regeneration by macrozooplankton was low compared to other tropical lakes and compared to microbesand microzooplankton in Lake Calado.     

Sex Differences in Plasma Steroid Concentrations and Singing Behaviour during Ontogeny in Canaries (Serinus canaria)

The relationship between the ontogenetic pattern of sex steroids and the differentiation of sexually dimorphic song in canaries of both sexes was studied. Songs were recorded to assess the temporal course of different developmental stages. Song parameters such as length and frequency of tours were measured. Parallel to behavioural observations, all birds were bled regularly every 20–30 days from the age of 15 days to day 235. The plasma samples were analyzed by RIA to measure testosterone (T), dihydrotestosterone (DHT) and estradiol-17β (E₂). The following results were obtained: 1) In young male canaries we distinguish three different stages of song development: subsong, starting at the age of 30 days, plastic song, and juvenile autumnal song finally giving way to the rigid and stable utterances of the reproductive period in next spring. During ontogeny the length and frequency of tours increase gradually. Female canaries were not observed singing regularly during their first year of life, whereas males sing very frequently. 2) Both sexes show tendencies to elevated titres of testosterone before the onset of juvenile moult. These titres correspond to those of paired males during the reproductive cycle. Song development is not correlated with the ontogenetic pattern of testosterone: the process of crystallization from the amorphic songs uttered by juveniles progresses gradually to the autumnal song in late autumn, when the titres of T in males are low (< 200 pg/ml). Female T and DHT levels during ontogeny correspond to those of the males. 3) There are sex differences in the estradiol pattern. Males show higher titres in several stages of development than females.     

The mixed xylem sap proteome of Fusarium oxysporum-infected tomato plants

Secreted proteins are known to play decisive roles in plant–fungus interactions. To study the molecular details of the interaction between the xylem-colonizing, plant-pathogenic fungus Fusarium oxysporum and tomato, the composition of the xylem sap proteome of infected tomato plants was investigated and compared with that of healthy plants. Two-dimensional gel separation and mass spectrometry yielded peptide masses and peptide sequences of 33 different proteins. Despite the absence of complete genome sequences of either tomato or F. oxysporum , 21 proteins were identified as tomato proteins and seven as fungal proteins. Thirteen of the tomato proteins were specific for infected plants. Sixteen tomato proteins were found in xylem sap for the first time, four of which were identified based on matches to expressed sequences only. Coding sequences for new proteins from F. oxysporum were identified through either direct matching to a database sequence, matching of peptide sequences to genome or expressed sequence tag databases of other Fusarium species, or PCR with degenerate primers on cDNA derived from infected plants followed by screening of a F. oxysporum BAC library. Together, these findings provide an excellent basis for further exploration of the interaction between xylem-colonizing pathogens and their hosts.