Contrasting effects of hemiparasites on ecosystem processes: can positive litter effects offset the negative effects of parasitism?

Hemiparasites are known to influence community structure and ecosystem functioning, but the underlying mechanisms are not well studied. Variation in the impacts of hemiparasites on diversity and production could be due to the difference in the relative strength of two interacting pathways: direct negative effects of parasitism and positive effects on N availability via litter. Strong effects of parasitism should result in substantial changes in diversity and declines in productivity. Conversely, strong litter effects should result in minor changes in diversity and increased productivity. We conducted field-based surveys to determine the association of Castilleja occidentalis with diversity and productivity in the alpine tundra. To examine litter effects, we compared the decomposition of Castilleja litter with litter of four other abundant plant species, and examined the decomposition of those four species when mixed with Castilleja. Castilleja was associated with minor changes in diversity but almost a twofold increase in productivity and greater foliar N in co-occurring species. Our decomposition trials suggest litter effects are due to both the rapid N loss of Castilleja litter and the effects of mixing Castilleja litter with co-occurring species. Castilleja produces litter that accelerates decomposition in the alpine tundra, which could accelerate the slow N cycle and boost productivity. We speculate that these positive effects of litter outweigh the effects of parasitism in nutrient-poor systems with long-lived hemiparasites. Determining the relative importance of parasitism and litter effects of this functional group is crucial to understand the strong but variable roles hemiparasites play in affecting community structure and ecosystem processes.     

Spermatotoxic effects of α-chlorohydrin in rats

This study was conducted to investigate the potential effects of α-chlorohydrin (ACH) on epididymal function and antioxidant system in male rats. The test chemical was administered to male rats by gavage at doses of 0, 3, 10, and 30 mg/kg/day for 7 days. Twenty-four male rats were randomly assigned to four experimental groups, with six rats in each group. Spermatotoxicity was assessed by measurement of reproductive organ weight, testicular sperm head count, epididymal sperm motility and morphology, histopathologic examination, and oxidative damage analysis in rats. At 30 mg/kg/day, an increase in the incidence of clinical signs, epididymis weight, and gross necropsy findings of the epididymis, a decrease in the sperm motility, and an increased incidence of histopathological changes of the epididymis were observed in a dose-dependent manner. At 10 mg/kg/day, an increased incidence of clinical signs and histopathological changes and decreased sperm motility were observed. In the oxidative damage analysis, an increase in the malondialdehyde concentration and a decrease in the glutathione content and glutathione peroxidase and catalase activities in the epididymal tissue were detected at ≥3 mg/kg/day. The results show that graded doses of ACH elicit depletion of the antioxidant defense system and that the spermatotoxicity of ACH may be due to the induction of oxidative stress.     

Anesthetic effects of a three-drugs mixture —comparison of administrative routes and antagonistic effects of atipamezole in mice—

The anesthetic mixture of medetomidine (MED), midazolam (MID) and butorphanol (BUT) produced anesthetic duration of around 40 minutes (min) in ICR mice. We reported that this anesthetic mixture produced almost the same anesthetic effects in both male and female BALB/c and C57BL/6J strains. Intraperitoneal (IP) administration of drugs has been widely used in mice. However, various injectable routes of the anesthetic mixture may cause different anesthetic effects. First, we examined effects of the anesthetic mixture by subcutaneous (SC) and intravenous (IV) injection compared to IP injection. After injection of the anesthetic mixture, administration of atipamezole (ATI) induced mice recovery from anesthesia. Secondly, we examined how different dosage and optimum injection timing of ATI affected mice recovery from anesthesia. We used an anesthetic score to measure anesthetic duration and a pulse oximeter to monitor vital signs under anesthesia. Usually, drugs from SC injection work more weakly than IP or IV injection. However, we found no significant differences of anesthetic duration among the three different injection routes. Antagonistic effects of ATI (0.3 mg/kg and 1.5 mg/kg) worked equally when administered at 30 min after injection of the anesthetic mixture. Antagonistic effects of ATI (1.5 mg/kg) were stronger than ATI (0.3 mg/kg) at 10 min after injection of the anesthetic mixture. The anesthetic mixture is a useful drug to induce nearly the same anesthetic effects by different injection routes and has an antagonist of ATI which helps mice quickly recover from anesthesia. These results may contribute to the welfare of laboratory animals.     

Scaling food chains in aquatic mesocosms: do the effects of depth override the effects of planktivory?

To assess the effects of physical dimension and planktivorous fish on phytoplankton standing crop, we repeated an experiment at different scales in plastic enclosures during summer 1995 in Lake Créteil, France. Enclosures were scaled for a constant surface (1.5 × 1.5 m) as depth was increased from 2.5 to 4.5 m. Even-link (zooplankton and phytoplankton) and odd-link (planktivorous fish, zooplankton and phytoplankton) food webs were established in both shallow and deep enclosures. Fish densities in the deep enclosures were scaled to allow comparisons with shallow ones for both in individuals m⁻² or individuals m⁻³. We explicitly designed this experiment to examine the scale-dependent behavior of the top-down mechanism of algal biomass control in lakes, and in particular to test the hypothesis of stronger cascading effects of fish on lower trophic levels at reduced depth. Both fish and enclosure size had highly significant effects on phytoplankton biomass over the duration of the experiment. No depth × fish interaction effects were observed. The presence of planktivorous fish enhanced phytoplankton biomass in both shallow and deep enclosures, although the reduction in depth generally produced a stronger effect. The mean concentration of chlorophyll a in the deep odd-link systems (ca 5 mg m⁻³) was lower than in the shallow even-link systems (ca 17 mg m⁻³). Statistical interpretation did not change when data were expressed as phytoplankton biomass per unit of surface area. Light limitation and zooplankton grazing are the most probable mechanisms explaining our results in these nutrient-enriched systems. Moreover, we found that the strength of the cascading effect of fish on plankton was not a function of depth. We believe that further studies on scaling effects should be conducted in order to improve our understanding of ecological patterns and to extrapolate results from micro/mesocosms to natural ecosystems. Received: 18 January 1999 / Accepted: 7 June 1999     

Comparison of the behavioral effects of β-endorphin and enkephalin analogs

The behavioral effects of β-endorphin, enkephalin analogs, morphine and etorphine were briefly compared. In the tail-flick test in mice and in the wet shake test in rats, β-endorphin and D-Ala²-D-Leu⁵-enkephalin had equal antinociceptive activity; D-Ala² -Met-enkephalinamide and D-Leu⁵-enkephalin were less active. The order of activity of the enkephalin analogs and opiate alkaloids for stimulating locomotor activity in mice paralleled their analgesic activities; β-endorphin, however, had only minimal stimulatory actions. Morphine sulfate, 50 μg injected into the periaqueductal gray, produced hyperactivity but this effect was not observed with etorphine or opioid peptides. By contrast, “wet dog” shakes was observed with the opioid peptides but not with either opiate alkaloid. These heterogenous behavioral responses, which were all antagonized by naloxone, indicate that multiple types of receptors mediate the effects of opiates in the central nervous system.     

Pervasive and strong effects of plants on soil chemistry: a meta-analysis of individual plant ‘Zinke’ effects

Plant species leave a chemical signature in the soils below them, generating fine-scale spatial variation that drives ecological processes. Since the publication of a seminal paper on plant-mediated soil heterogeneity by Paul Zinke in 1962, a robust literature has developed examining effects of individual plants on their local environments (individual plant effects). Here, we synthesize this work using meta-analysis to show that plant effects are strong and pervasive across ecosystems on six continents. Overall, soil properties beneath individual plants differ from those of neighbours by an average of 41%. Although the magnitudes of individual plant effects exhibit weak relationships with climate and latitude, they are significantly stronger in deserts and tundra than forests, and weaker in intensively managed ecosystems. The ubiquitous effects of plant individuals and species on local soil properties imply that individual plant effects have a role in plant–soil feedbacks, linking individual plants with biogeochemical processes at the ecosystem scale.     

Some inhibitory effects of (?)-emetine on growth of Ehrlich ascites carcinoma

(−)-Emetine has little or no effect on O₂ consumption of Ehrlich ascites-cell suspensions or on the viability of transplanted Ehrlich ascites-tumour cells exposed to, or incubated with, the drug in vitro before inoculation into new-host mice. (−)-Emetine administered as a single injection to mice bearing Ehrlich ascites-tumour cells slows the growth rate of the tumour. The subcutaneous or intraperitoneal injection of the drug depresses protein and DNA synthesis of the tumour cells in vivo in a reversible manner. Mice bearing ascitic sarcoma 180 or Ehrlich ascites-tumour cells when given a course of treatment with (−)-emetine or (−)-O-methyltubulosine have a substantially lower tumour load than untreated controls and correspondingly longer survival times.     

Characteristics and effects of specific peptides on heat-induced aggregation of β-lactoglobulin

A bovine β-lactoglobulin hydrolysate, obtained by the hydrolysis by the Glu specific enzyme Bacillus licheniformis protease (BLP), was fractionated at pH 7.0 into a soluble and an insoluble fraction and characterized by LC-MS. From the 26 peptides identified in the soluble fraction, five peptides (A[f97-112] = [f115-128], AB[f1-45], AB[f135-157], AB[f135-158], and AB[f138-162]) bound to β-lactoglobulin at room temperature. After heating of β-lactoglobulin in the presence of peptides, eight peptides were identified in the pellet formed, three of them belonging to the previously mentioned peptides. Principle component analysis revealed that the binding at room temperature (to β-lactoglobulin) was related to the total hydrophobicity and the total charge of the peptides. The binding to the unfolded protein could not be attributed to distinct properties of the peptides. The presence of the peptides caused a 50% decrease in denaturation enthalpy (from 148 ± 3 kJ/mol for the protein alone to 74 ± 2 kJ/mol in the presence of peptides), while no change in secondary structure or denaturation temperature was observed. At temperatures <85 °C, the addition of peptides resulted in a 30-40% increase of precipitated β-lactoglobulin. At pH < 6, no differences in the amount of aggregated β-lactoglobulin were observed, which indicates the lack of binding of peptides to β-lactoglobulin at those pH values as was also observed by SELDI-TOF-MS. Although only a few peptides were found to participate in aggregation, suggesting specificity, principal component analysis was unable to identify specific properties responsible for this.     

The effects of a load of phen?lalanine on glucose metabolism

The clinical and experimental hyperphenylalaninemic conditions seem associated with disorders of carbohydrates metabolism. Examples are the increased liver glucose turnover and the glycogen depletion under Phenylalanine load and the hyperexcretion of glucose in the urine of PKU children. We studied the effects of an acute load of Phenylalanine on Glucose-3-H3 kinetics and plasma glucose levels in adult male Wistar rats. The effects of the load were very slow and after 40 minutes we observed an increase in the rate of plasma glucose production (Ra), that in normal animals in an almost exclusive liver function. As result of this glucose production there was a modest increase in plasma glucose levels.     

Synthesis and evaluation of cytotoxic effects of novel α-methylenelactone tetracyclic diterpenoids

A series of tetracyclic diterpenoids bearing the α-methylenelactone group have been synthesized and screened for their in vitro anti-tumor activities against six human cancer cell lines. The results showed that compounds 1c, 2a and 2b exhibited significant cytotoxicity superior to the positive control doxorubicin hydrochloride against MDA-MB-231, K562 and HepG2 cell lines. In particular, compound 2b was identified as the most promising anticancer agent against HepG2 cells with IC(50) value of 0.09μM.     

Protective effects of evodiamine in experimental paradigm of Alzheimer’s disease

Evodiamine, a major component of Evodia rutaecarpa, has been reported to possess various pharmacological activities, including anti-inflammatory, antioxidative stress, and neuroprotective effects. Our previous study has shown that the potential effects of evodiamine on the learning and memory impairments in the transgenic mouse model of Alzheimer’s disease (AD). The present study was designed to investigate neuroprotective mechanism and therapeutic potential of evodiamine against intracerebroventricular streptozotocin (ICV-STZ)-induced experimental sporadic Alzheimer’s disease in mice. STZ was injected twice intracerebroventrically (3 mg/kg ICV) on alternate days (day 1 and day 3) in mice. Daily oral administration with evodiamine (50 or 100 mg/kg per day) starting from the first dose of STZ for 21 days showed an improvement in STZ induced cognitive deficits as assessed by novel object recognition and Morris water maze test. Evodiamine significantly decreased STZ induced elevation in acetylcholinesterase activity and malondialdehyde level, and significantly increased STZ induced reduction in glutathione activities and superoxide dismutase activities in the hippocampus compared to control. Furthermore, evodiamine inhibited significantly glial cell activation and neuroinflammation (TNF-α, IL-1β, and IL-6 levels) in the hippocampus. Moreover, evodiamine increased the activity of AKT/GSK-3β signalling pathway and inhibited the activity of nuclear factor κB. In summary, our study suggests that evodiamine can be a novel therapeutic agent for the management of sporadic AD.     

Toxic effects of antimalarial drugs in Paramecium : role of calcium channels

The antimalarial drugs, quinacrine, quinine and mefloquine, as well as the structurally-similar compound, W-7, inhibit calcium-dependent backward swimming and calcium currents in Paramecium calkinsi. These drugs are also toxic to paramecia at high concentrations. Therefore, one site of toxic action of the drugs may be the calcium channel. To test this hypothesis, the toxicity of the antimalarials and W-7 was compared in paramecia with and without calcium channels. Since calcium channels are located on the cilia, calcium channels were removed from the paramecia by deciliating the cells. Deciliated cells were found to be less susceptible to the lethal effects of the antimalarials and W-7 than their ciliated counterparts. Moreover, Pawns, mutants of P. tetraurelia that possess cilia but lack functional calcium channels, were also less susceptible to the antimalarials than wild-type cells. Thus, calcium channels may be one site of toxic action of the antimalarial drugs in paramecia and perhaps in other protists. Accepted: 27 December 1996     

Do bioassays adequately predict ecological effects of pollutants?

With some notable exceptions, such as the echinoderm and oyster larvae tests, the species traditionally used in bioassays are not sufficiently sensitive to detect subtle ecological effects of pollutants. It is suggested that by using ecological criteria, species can be identified from any pollution gradient that are sensitive to subtle effects of pollution. Examples are given using gradients of oil, sewage and titanium dioxide pollution, showing how ecologically sensitive species for use in laboratory bioassays can be selected objectively.Many marine molluscs show microgrowth bands, which can be used as in situ field bioassays. An example is given using the bivalve Cerastoderma edule.     

Cross-seeding effects of amyloid β-protein and α-synuclein

J. Neurochem. (2012) 122, 883-890. ABSTRACT: Amyloid β-protein (Aβ) and α-synuclein (αS) are the primary components of amyloid plaques and Lewy bodies (LBs), respectively. Previous in vitro and in vivo studies have suggested that interactions between Aβ and αS are involved in the pathogenesis of Alzheimer's disease and LB diseases. However, the seeding effects of their aggregates on their aggregation pathways are not completely clear. To investigate the cross-seeding effects of Aβ and αS, we examined how sonicated fibrils or cross-linked oligomers of Aβ40, Aβ42, and αS affected their aggregation pathways using thioflavin T(S) assay and electron microscopy. Fibrils and oligomers of Aβ40, Aβ42, and αS acted as seeds, and affected the aggregation pathways within and among species. The seeding effects of αS fibrils were higher than those of Aβ40 and Aβ42 fibrils in the Aβ40 and Aβ42 aggregation pathways, respectively. We showed that Aβ and αS acted as seeds and affected each other's aggregation pathways in vitro, which may contribute to our understanding of the molecular mechanisms of interactions between Alzheimer's disease and LB diseases pathologies.     

Spirituality: an overlooked predictor of placebo effects?

Empirical findings have identified spirituality as a potential health resource. Whereas older research has associated such effects with the social component of religion, newer conceptualizations propose that spiritual experiences and the intrapersonal effects that are facilitated by regular spiritual practice might be pivotal to understanding potential salutogenesis. Ongoing studies suggest that spiritual experiences and practices involve a variety of neural systems that may facilitate neural 'top-down' effects that are comparable if not identical to those engaged in placebo responses. As meaningfulness seems to be both a hallmark of spirituality and placebo reactions, it may be regarded as an overarching psychological concept that is important to engaging and facilitating psychophysiological mechanisms that are involved in health-related effects. Empirical evidence suggests that spirituality may under certain conditions be a predictor of placebo response and effects. Assessment of patients' spirituality and making use of various resources to accommodate patients' spiritual needs reflect our most current understanding of the physiological, psychological and socio-cultural aspects of spirituality, and may also increase the likelihood of eliciting self-healing processes. We advocate the position that a research agenda addressing responses and effects of both placebo and spirituality could therefore be (i) synergistic, (ii) valuable to each phenomenon on its own, and (iii) contributory to an extended placebo paradigm that is centred around the concept of meaningfulness.     

Complex effects of 17β-estradiol on mitochondrial function

Existing literature on estradiol indicates that it affects mitochondrial functions at low micromolar concentrations. Particularly blockade of the permeability transition pore (PTP) or modulation of the enzymatic activity of one or more complexes of the respiratory chain were suspicious. We prepared mitoplasts from rat liver mitochondria (RLM) to study by single-channel patch-clamp techniques the PTP, and from rat astrocytes to study the potassium BK-channel said to modulate the PTP. Additionally, we measured respiration of intact RLM. After application of 17β-estradiol (βE) our single-channel results reveal a transient increase of activity of both, the BK-channel and the PTP followed by their powerful inhibition. Respiration measurements demonstrate inhibition of the Ca(2+)-induced permeability transition, as well, though only at higher concentrations (≥30μM). At lower concentrations, we observed an increase of endogenous- and state 2-respiration. Furthermore, we show that βE diminishes the phosphorylating respiration supported by complex I-substrates (glutamate/malate) or by the complex II-substrate succinate. Taken together the results suggest that βE affects mitochondria by several modes, including partial inhibition of the activities of ion channels of the inner membrane and of respiration. This article is part of a Special Issue entitled: 17th European Bioenergetics Conference (EBEC 2012).     

Molecular chaperone α-crystallin prevents detrimental effects of neuroinflammation

Silver nitrate administration stimulates immune activation, inflammation and deterioration in cell function. It is well established that hippocampal and cortical tissue are susceptible to degeneration in responses to insult such as oxidative stress or infection. This study was designed to investigate the prophylactic effect of α-crystallin, a major chaperone lens protein comprising of α-A and α-B subunits in inflammation induced mice. Mice were divided into three groups (n = 6 in each), control, inflammation and α-crystallin treated. Our result shows that α-crystallin pretreatment effectively diminished systemic inflammation induced glial fibrillary acidic protein (GFAP) and nuclear factor kappa B (NFκB) expression in the mice neocortex, reversed elevated intracellular calcium levels, acetylcholine esterase activity and depletion of glucose. Furthermore it also significantly prevented nitric oxide (P < 0.05) and lipid peroxide production in the plasma, liver, neocortex and hippocampus of the inflammation-induced mice. In order to demonstrate the direct OH and nitric oxide radical scavenging ability of α-crystallin, an In vitro experiment using primary astrocyte culture subjected to lipopolysaccharide (LPS), a well-known inflammatory stimuli were also carried out. This study reiterates that α-crystallin therapy may serve as a potent pharmacological agent in neuroinflammation.