Effects of network and dynamical model structure on species persistence in large model food webs

Four models of network structure are combined with models of bioenergetic dynamics to study the role of food web topology and nonlinear dynamics on species coexistence in complex ecological networks. Network models range from the highly structured niche model to loosely constrained energetically feasible random networks. Bioenergetic models differ in how they represent primary production, functional responses, and consumption by generalists. Network structure weakly influenced the ability of species to coexist. Species persistence is strongly affected by functional responses and generalists’ consumption rates but weakly affected by models and amounts of primary production. Despite these generalities, specific mechanisms that determine persistence under one dynamical regime, such as top-down control by consumers, may play an insignificant role under different dynamical conditions. Future research is needed to strengthen the weak empirical basis for various functional forms and parameter values that strongly influence whether species can coexist in complex food webs. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Use of an anaerobic chamber environment for the assay of endogenous cellular protein-tyrosine phosphatase activities

Protein-tyrosine phosphatases (PTPases) have a catalytic cysteine residue whose reduced state is integral to the reaction mechanism. Since exposure to air can artifactually oxidize this highly reactive thiol, PTPase assays have typically used potent reducing agents to reactivate the enzymes present; however, this approach does not allow for the measurement of the endogenous PTPase activity directly isolated from the in vivo cellular environment. Here we provide a method for using an anaerobic chamber to preserve the activity of the total PTPase complement in a tissue lysate or of an immunoprecipitated PTPase homolog to characterize their endogenous activation state. Comparison with a sample treated with biochemical reducing agents allows the determination of the activatable (reducible) fraction of the endogenous PTPase pool. Published: June 11, 2002.     

Achim Trebst,my senior,and our joint research

In this tribute, I offer my best wishes to Achim Trebst on his 80th birthday on June 9, 2009. At the invitation of Govindjee, I present here a perspective of some of our joint research during 1970s through 2000s.     

Effects of etretinate on the distribution of elements in rats

We studied in the rat the effects of the drug etretinate (Tigason), given at three doses 3, 10, and 30 mg/kg body wt for 1 mo, on the concentrations of Na, K, Ca, Mg, Fe, S, P, Cu, and Zn in the plasma, brain, thymus, heart, liver, lung, kidney, testicle, muscle, and bone. The elements were simultaneously determined in tissues after nitric acid dissolution by inductively coupled plasma emission spectrometry using a JY 48 instrument. At the dose of 3 mg/kg, etretinate did not induce any statistically significant modifications of the element distribution. At the dose of 10 mg/kg, the main observed modifications were in plasma an increase of copper (+38%) and a decrease of zinc (-25%). At the highest dose of 30 mg/kg, some variations of the concentrations of elements in tissues were observed. But, on no account did retinoids induce an alteration of the mineral composition of bone, despite obvious macroscopic bone alterations.     

MPEC: an important gene in the chlorophyll biosynthesis pathway in photosynthetic organisms

One of the least understood enzymatic steps in chlorophyll biosynthesis is the formation of isocyclic ring, which is catalyzed by the Mg-protoporphyrin IX monomethyl ester (MgPME) cyclase that is involved in the conversion of MgPME to protochlorophyllide. Several genes encoding part of this enzyme have been identified and functional analysis of them has been performed. The enzyme plays important roles in higher plants and photosynthetic bacteria. The review focuses on the current knowledge of MgPME cyclase coding genes, with emphasis on their organization, expression pattern, and functional analysis obtained from mutants.     

Effects of doxorubicin on the sensitivity of L1210 leukemia cells to deformation-associated trauma

Most of the cancer cells arrested in the microcirculation during hematogenous metastasis are rapidly killed; one major mechanism is surface-membrane rupture, associated with the mechanical deformation of cancer cells in capillaries. The feasibility of increasing the susceptibility of cancer cells to lethal, deformation-associated trauma by doxorubicin, was tested in an in vitro mechanical model system, by filtering suspensions of L1210 leukemia cells through 8-μm pore-size Nuclepore® membranes, with or without prior incubation with 10^-7M doxorubicin. The results showed that mechanically-induced loss of cancer cells immediately after filtration was increased from 18 to 55% in cells previously exposed to doxorubicin for 48 h. The results indicate the feasibility of chemotherapeutic enhancement of the mechanical killing-action of the microvasculature as a potential rate-regulator of hematogenous metastasis.     

Reproductive seasonality and maturity of male Neophocaena phocaenoides asiaeorientalis in captivity: A case study based on the hormone evidence

To provide hormone evidence on reproductive seasonality and maturity of the Yangtze finless porpoise, the authors monitored the monthly variations of serum reproductive hormones of a male Yangtze finless porpoise in captivity via radioimmunoassay from 1997 to 2003. It was demonstrated that the immature animal had a serum T level of 28–101?ng?dL^?1 (65?±?52?ng?dL^?1), reached puberty with the serum T concentration ranging between 250 and 590?ng?dL^?1 (390?±?130?ng?dL^?1), and attained reproductive maturity when the serum T level went beyond 1120?±?180?ng?dL^?1 in the breeding season. The body length growth of the animal showed a pattern similar to the serum T variations during its adolescent period from the age of 4 to 6 years. Moreover, the serum T concentration of the male porpoise exhibited significant seasonal variations, indicating that its breeding season may start as early as March and end as late as September.     

Cadmium effects on the organization of microtubular cytoskeleton in interphase and mitotic cells of Allium sativum

We have investigated the effects of cadmium on the microtubular (MT) cytoskeleton in the root tip cells of Allium sativum L. using indirect immunofluorescence microscopy. Cd affected the mechanisms controlling the organization of MT cytoskeleton, as well as tubulin assembly/disassembly processes. Cd induced the formation of abnormal MT arrays, consisting of discontinuous wavy MTs or short MT fragments at the cell periphery. Cadmium caused irregular nuclear disorder in cells where the MT organization and function was disturbed. Furthermore, with increased Cd concentration and duration of treatment the MTs depolymerized more severely, the frequency of abnormal cell increased and the mitotic index decreased progressively. The above findings showed that MT cytoskeleton is one of target sites of Cd toxicity in root tip cells.     

Effects of evening and nighttime leaf wetting on stomatal behavior of Cryptomeria japonica growing in dry soil

To examine the hypothesis that stomatal behavior of plants in dry soil is influenced by a slow recovery from daytime water deficit, we studied the effect of repeated wetting of leaves during evening and night in Cryptomeria japonica seedlings grown in dry soil. After 7 and 10 days of leaf wetting treatment the midday leaf water potential decreased and the transpiration rate increased, respectively. Therefore, we suggest that rapid recovery from daytime water deficit could weaken the water conserving stomatal behavior that adapts to drought conditions in the roots.     

Synthesis and Characterization of Pectin/PVP Hydrogel Membranes for Drug Delivery System

The purpose of the present study was to develop and design pectin and polyvinyl pyrrolidone (PVP) blended hydrogel membranes (PEVP), with different pectin: PVP ratios (1:0.2, 1:0.4, 1:0.6, 1:0.8 and 1:1 w/w), which were prepared by using a conventional solution casting technique. An attempt has been made to characterize the hydrogel membranes by various instrumental techniques like, FTIR (Fourier transform infrared) spectroscopy, X-ray diffraction (XRD), Differential scanning calorimetry (DSC), tensile strength test and scanning electron microscopy (SEM). The release patterns of the drug (salicylic acid) from the hydrogel membrane were done in three different release mediums (pH 1.4, pH 7.4 and distilled water) and samples were analyzed spectrophotometrically at 294 nm wavelength on a UV Vis spectrophotometer. MTT assay was done to ensure cytocompatibility of the pectin/PVP hydrogel membranes using B16 melanoma cells. FTIR spectroscopy indicated the presence of secondary amide (I) absorption bands. The XRD study shows decrease in crystallinity of the hydrogel membranes with increase in PVP ratio. DSC study shows an increase in T _g of pectin after blending with PVP. It was found that tensile strength increases with increasing PVP ratios in the hydrogel membranes. The prepared hydrogel membranes were found to be biocompatible with B16 melanoma cells.     

Prediction of early termination from the self-regulatory treatment of chronic headache

The ability of demographic, psychological testing and history information to predict which patients will terminate early from nonpharmacological treatment of headache (relaxation and biofeedback) was tested. Information from each of these areas was initially examined for differences between dropouts and treatment completers using univariate analyses. These analyses were followed by a canonical discriminate function analysis that predicted whether patients would complete treatment or drop out. Information from the three predictor sets combined resulted in 77.4% of the patients being correctly classified.This research was supported by a grant from the NINCDS, NS15235.     

Response

The offer of the fast food company gives rise to suspicion. This seems to be based on unfounded stereotypes, however. This paper argues that we need to preserve choices in taking particular courses of action. There is nothing inherently wrong in fast food consumption so long as consumers are made aware of the importance of weight management and proper nutrition.     

Feeding behaviour,feed selectivity and growth studies of mangrove killifish, <Emphasis Type="Italic">Kryptolebias marmoratus</Emphasis>, larvae using various live and formulated feeds

Nine types of live foods viz. L, S and SS morphotypes of Brachionus plicatilis sp. complex, first instar Artemia franciscana, Fabrea salina, Acartia tsuensis, Tigriopus japonicus, Diaphanosoma celebensis, Moina mongolica and a formulated feed of two sizes (400 and 700 μm) were used to observe feeding behaviour and growth of mangrove killifish, Kryptolebias marmoratus. Behavioural observations were made for one hour on days 0, 1, 5, and 10 after hatching. Focus, unsuccessful and successful attacks and vomit were noted. With rotifers L, S and SS types and newly hatched Artemia nauplii as food, all the larvae showed maximum feeding success throughout the experimental period. Larvae did not consume any of the 700 μm artificial diet. Vomiting was noticed on capturing the ciliate Fabrea and 400 μm artificial diets. Rotifers were ingested in greater numbers. SS-type rotifers were consumed in largest number (209.2/h per individual) on day 10. Significantly greater growth was observed after 10 days rearing with L type rotifer, Artemia nauplii, T. japonicus, A. tsuensis, M. mongolica, D. celebensis, and a mixture of L type rotifer and F. salina (Tukey–Kramer post hoc test, P < 0.05). Feed selectivity experiments on days 0, 1, 5 and 10 revealed that killifish larvae feed preferentially on Artemia nauplii and rotifers from a mixture of Artemia nauplii, rotifers, A. tsuensis, T. japonicus, D. celebensis and M. mongolica. Techniques for culturing various zooplankton at small-scales are also described.     

Age and gender differences in the relationship between heart rate reactivity and elevated serum lipids

Data on serum lipids and heart rate reactivity to a standardized mental arithmetic stressor were collected on 54 healthy men and 73 healthy women. Subjects' ages ranged from 18 to 61 years, allowing analysis of data from both young and older subgroups. MANOVA revealed that age was directly associated with elevated lipids in men and women. There was no significant relationship between reactivity and lipids for either older or young men. Conversely, young women showed a significant direct relationship between reactivity and Total Cholesterol and LDL, but this was not present for older women. Implications of these data for the previously reported hypothetical relationship between reactivity and lipids are discussed. Limitations of the study are examined, and future directions for research suggested.I wish to thank Dianne Vella for her assistance in aspects of data-collection. This research was supported by grant No. 900946 from the National Health & Medical Research Council.     

Lake trout (<Emphasis Type="Italic">Salvelinus namaycush</Emphasis>) spawning behaviour: the evolution of a new female strategy

A video camera inside an underwater housing was used to record the spawning activities of lake trout, Salvelinus namaycush, in Kushog Lake, Ontario (Canada). Contrary to the commonly accepted belief describing lake trout as the only salmonine to spawn exclusively at night, the recordings were taken during the day. Lake trout spawning behaviour is described in detail and compared with other salmonine species. The loss of female “nest-building” and assumption of a novel itinerant strategy during which females travel across the breeding grounds accompanied by a group of males, is considered to be an important change in the evolution of the lake trout’s unique mode of spawning.     

Base catalysed isomerisation of aldoses of the arabino and lyxo series in the presence of aluminate

Base-catalysed isomerisation of aldoses of the arabino and lyxo series in aluminate solution has been investigated. L-Arabinose and D-galactose give L-erythro-2-pentulose (L-ribulose) and D-lyxo-2-hexulose (D-tagatose), respectively, in good yields, whereas lower reactivity is observed for 6-deoxy-D-galactose (D-fucose). From D-lyxose, D-mannose and 6-deoxy-L-mannose (L-rhamnose) are obtained mixtures of ketoses and C-2 epimeric aldoses. Small amounts of the 3-epimers of the ketoses were also formed. 6-Deoxy-L-arabino-2-hexulose (6-deoxy-L-fructose) and 6-deoxy-L-glucose (L-quinovose) were formed in low yields from 6-deoxy-L-mannose and isolated as their O-isopropylidene derivatives. Explanations of the differences in reactivity and course of the reaction have been suggested on the basis of steric effects.     

Prenylated flavonoids and total extracts from Morus nigra L. root bark inhibit in vitro growth of plant pathogenic fungi

Total extracts and kuwanon G from Morus nigra root bark showed antifungal activity against several phytopathogenic fungi, with minimal inhibitory concentration (MIC₅₀) ranging from 32 to 128 μg/ml and from 16 to 64 μg/ml, respectively. Acetonic extracts inhibited 60% B. cinerea biofilm formation at concentration of 128 μg/ml.     

Porous bone morphogenetic protein-2 microspheres: Polymer binding and in vitro release

This research compared the binding and release of recombinant human bone morphogenetic protein 2 (rhBMP-2) with a series of hydrophobic and hydrophilic poly-lactide-co-glycolide (PLGA) copolymers. Porous microspheres were produced via a double emulsion process. Binding and incorporation of protein were achieved by soaking microspheres in buffered protein solutions, filtering, and comparing protein concentration remaining to nonmicrosphere-containing samples. Protein release was determined by soaking bound microspheres in a physiological buffer and measuring protein concentration (by reversed-phase high-performance liquid chromatography) in solution over time. Normalized for specific surface area and paired by polymer molecular weight. microspheres made from hydrophilic 50∶50 or 75∶25 PLGA bound significantly more protein than microspheres made from the corresponding hydrophobic PLGA. Increased binding capacity correlated with higher polymer acid values. With certain polymers, rhBMP-2 adsorption was decreased or inhibited at high protein concentration, but protein loading could be enhanced by increasing the protein solution:PLGA (volume:mass) ratio or by repetitive soaking. Microspheres of various PLGAs released unbound protein in 3 days, whereas the subsequent bound protein release corresponded to mass loss. RhBMP-2 binding to PLGA was controlled by the acid value, protein concentration, and adsorption technique. The protein released in 2 phases: the first occurred over 3 days regardless of PLGA used and emanated from unbound, incorporated protein, while the second was controlled by mass loss and therefore was dependent on the polymer molecular weight. Overall, control of rhBMP-2 delivery is achievable by selection of PLGA microsphere carriers. Published: October, 7, 2001.