A physiological analogy of the niche for projecting the potential distribution of plants

Aim  To develop a physiologically based model of the plant niche for use in species distribution modelling. Location  Europe. Methods  We link the Thornley transport resistance (TTR) model with functions which describe how the TTR’s model parameters are influenced by abiotic environmental factors. The TTR model considers how carbon and nutrient uptake, and the allocation of these assimilates, influence growth. We use indirect statistical methods to estimate the model parameters from a high resolution data set on tree distribution for 22 European tree species. Results  We infer, from distribution data and abiotic forcing data, the physiological niche dimensions of 22 European tree species. We found that the model fits were reasonable (AUC: 0.79–0.964). The projected distributions were characterized by a false positive rate of 0.19 and a false negative rate 0.12. The fitted models are used to generate projections of the environmental factors that limit the range boundaries of the study species. Main conclusions  We show that physiological models can be used to derive physiological niche dimensions from species distribution data. Future work should focus on including prior information on physiological rates into the parameter estimation process. Application of the TTR model to species distribution modelling suggests new avenues for establishing explicit links between distribution and physiology, and for generating hypotheses about how ecophysiological processes influence the distribution of plants.     

The mannoprotein of Saccharomyces cerevisiae is an effective bioemulsifier

The mannoprotein which is a major component of the cell wall of Saccharomyces cerevisiae is an effective bioemulsifier. Mannoprotein emulsifier was extracted in a high yield from whole cells of fresh bakers' yeast by two methods, by autoclaving in neutral citrate buffer and by digestion with Zymolase (Miles Laboratories; Toronto, Ontario, Canada), a beta-1,3-glucanase. Heat-extracted emulsifier was purified by ultrafiltration and contained approximately 44% carbohydrate (mannose) and 17% protein. Treatment of the emulsifier with protease eliminated emulsification. Kerosene-in-water emulsions were stabilized over a broad range of conditions, from pH 2 to 11, with up to 5% sodium chloride or up to 50% ethanol in the aqueous phase. In the presence of a low concentration of various solutes, emulsions were stable to three cycles of freezing and thawing. An emulsifying agent was extracted from each species or strain of yeast tested, including 13 species of genera other than Saccharomyces. Spent yeast from the manufacture of beer and wine was demonstrated to be a possible source for the large-scale production of this bioemulsifier.     

A Correspondence between Individual Differences in the Brain's Intrinsic Functional Architecture and the Content and Form of Self-Generated Thoughts

Although neural activity often reflects the processing of external inputs, intrinsic fluctuations in activity have been observed throughout the brain. These may relate to patterns of self-generated thought that can occur while not performing goal-driven tasks. To understand the relationship between self-generated mental activity and intrinsic neural fluctuations, we developed the New York Cognition Questionnaire (NYC-Q) to assess the content and form of an individual''s experiences during the acquisition of resting-state fMRI data. The data were collected as a part of the Nathan Kline Rockland Enhanced sample. We decomposed NYC-Q scores using exploratory factor analysis and found that self-reported thoughts clustered into distinct dimensions of content (future related, past related, positive, negative, and social) and form (words, images, and specificity). We used these components to perform an individual difference analysis exploring how differences in the types of self-generated thoughts relate to whole brain measures of intrinsic brain activity (fractional amplitude of low frequency fluctuations, regional homogeneity, and degree centrality). We found patterns of self-generated thoughts related to changes that were distributed across a wide range of cortical areas. For example, individuals who reported greater imagery exhibited greater low frequency fluctuations in a region of perigenual cingulate cortex, a region that is known to participate in the so-called default-mode network. We also found certain forms of thought were associated with other areas, such as primary visual cortex, the insula, and the cerebellum. For example, individuals who reported greater future thought exhibited less homogeneous neural fluctuations in a region of lateral occipital cortex, a result that is consistent with the claim that particular types of self-generated thought depend on processes that are decoupled from sensory processes. These data provide evidence that self-generated thought is a heterogeneous category of experience and that studying its content can be helpful in understanding brain dynamics.     

Human Cytidine Triphosphate Synthetase 1 Interacting Proteins

We investigated the interacting proteins and intracellular localization of CTP synthetase 1 (CTPS1) in mammalian cells. CTPS1 interacted with a GST- peptidyl prolyl isomerase, Pin1 fusion (GST-Pin1) in a Ser 575 (S575) phosphorylation-dependent manner. Immunoprecipitation experiments demonstrated that CTPS1 also bound tubulin, and thirteen additional coimmunoprecipitating proteins were identified by mass spectrometry. Immunolocalization experiments showed that tubulin and CTPS1 colocalized subcellularly. Taxol treatment enhanced this but cotreatment of cells with the CTPS inhibitor, cyclopentenyl cytosine (CPEC), and taxol failed to disrupt the colocalization. Thus, these studies provide novel information on the potential interacting proteins that may regulate CTPS1 function or intracellular localization.     

A generic algorithm for finding restriction sites within DNA sequences

This paper describes a generic algorithm for finding restrictionsites within DNA sequences. The ‘genericity’ ofthe algorithm is made possible through the use of set theory.Basic elements of DNA sequences, i.e. nucleotides (bases), arerepresented in sets, and DNA sequences, whether specific, ambiguousor even protein-coding, are represented as sequences of thosesets. The set intersection operation demonstrates its abilityto perform pattern-matching correctly on various DNA sequences.The performance analysis showed that the degree of complexityof the pattern matching is reduced from exponential to linear.An example is given to show the actual and potential restrictionsites, derived by the generic algorithm, in the DNA sequencetemplate coding for a synthetic calmodulin. Received on October 2, 1990; accepted on December 18, 1990     

Asymmetry of the phospholipid bilayer of rat liver endoplasmic reticulum

The phospholipids of intact microsomal membranes were hydrolysed 50% by phospholipase C of Clostridium welchii, without loss of the secretory protein contents of the vesicle, which are therefore not permeable to the phospholipase. Phospholipids extracted from microsomes and dispersed by sonication were hydrolysed rapidly by phospholipase C-Cl. welchii with the exception of phosphatidylinositol. Assuming that only the phospholipids of the outside of the bilayer of the microsomal membrane are hydrolysed in intact vesicles, the composition of this leaflet was calculated as 84% phosphatidylcholine, 8% phosphatidylethanolamine, 9% sphingomyelin and 4% phosphatidylserine, and that of the inner leaflet 28% phosphatidylcholine, 37% phosphatidylethanolamine, 6% phosphatidylserine and 5% sphingomyelin. Microsomal vesicles were opened and their contents released in part by incubation with deoxycholate (0.098%) lysophosphatidylcholine (0.005%) or treatment with the French pressure cell. Under these conditions, hydrolysis of the phospholipids by phospholipase C-Cl. welchii was increased and this was mainly due to increased hydrolysis of those phospholipids assigned to the inner leaflet of the bilayer, phosphatidylethanolamine and phosphatidylserine. Phospholipase A₂ of bee venom and phospholipase C of Bacillus cereus caused rapid loss of vesicle contents and complete hydrolysis of the membrane phospholipids, with the exception of sphingomyelin which is not hydrolysed by the former enzyme.