Central organization of common inhibitory motoneurons in the locust: role of afferent signals from leg mechanoreceptors

Intracellular recordings of mesothoracic common inhibitory neurons (CI₁, CI₂ and CI₃) were made while tactile hairs of the middle legs of locusts (Locusta migratoria) were mechanically stimulated. Generally the three common inhibitory neurons were excited by stimulation of tactile hairs on the ventral and dorsal surface of femur and tibia. The response pattern of all three CI neurons was similar suggesting that they work as a functional unit. Touching hairs on the dorsal surface of tibia and tarsus in some cases led to inhibition of CIs. The connection between sensory cells of tactile hairs and common inhibitory neurons is polysynaptic.To identify interneurons which mediate afferent signals, simultaneous intracellular recordings from CIs and interneurons were made. Different spiking interneurons were identified which made excitatory or inhibitory monosynaptic connections with CIs. Interneurons with inhibitory input to CIs belonged to the ventral midline group of spiking local interneurons. Behavioral and electrophysiological results indicate that reflex movements of the leg are accompanied by activity of CI neurons. Further it appears that CI activity is inhibited when reflex movements of the leg are actively suppressed by the animal.Abbreviations CI common inhibitor - IN interneuron - LY Lucifer Yellow     

Expression of CNTF/LIF‐receptor components and activation of STAT3 signaling in axotomized facial motoneurons: Evidence for a sequential postlesional function of the cytokines

Several lines of evidence suggest that ciliary neurotrophic factor (CNTF) and leukemia inhibitory factor (LIF) are important for the survival and regeneration of axotomized motoneurons. To investigate the role of CNTF/LIF signaling in regenerative responses of motoneurons, we studied the expression of the three receptor components, CNTF receptor α (CNTFRα), LIF receptor β (LIFRβ), and gp130, and the activation of the STAT3 signal transduction pathway in the rat facial nucleus following peripheral nerve transection. As shown by in situ hybridization and immunoblotting, axotomy resulted in a rapid down‐regulation of CNTFRα mRNA expression within 24 h and a concomitant massive up‐regulation of LIFRβ mRNA and protein in the lesioned motoneurons. The altered mRNA levels were maintained for 3 weeks but had returned back to control levels by 6 weeks postlesion after successful regeneration. In contrast, mRNA levels remained in the lesioned state during the 6‐week period studied, when regeneration was prevented by nerve resection. Significant lesion‐induced changes in gp130 mRNA levels were not detectable. Rapid (within 24 h) and sustained (for at least 5 days) activation of STAT3 in axotomized facial motoneurons was revealed by demonstrating the phosphorylation and nuclear translocation of the protein using immunocytochemistry and immunoblotting. In agreement with previous studies showing a complementary regulation of CNTF and LIF in the lesioned facial nerve, our observations on the postlesional regulation of CNTF/LIF receptor components in the facial nucleus indicate a direct and sequential action of the two neurotrophic proteins on axotomized facial motoneurons. © 1999 John Wiley & Sons, Inc. J Neurobiol 41: 559–571, 1999     

A regression model of the relationship between locust seedling growth and soil conditions

The relationship between locust (Robinia pseudoacacia L.) biomass and soil physico-chemical properties can be expressed by a multivariate regression equation. The best equation formed through a stepwise regression method indicated that acidity and available P were the main factors which influenced plant growth. The role of available P reflected its cooperative relationship with available Mo and available K separately. Available N, available K and CaCO₃ also played very important roles and the concerted effects of available Mo with CaCO₃, CO₂ and total N separately had obviously cooperative effects to promote plant growth. Greater locust growth occurred in neutral, low calcareous and weakly acid soil, poorer growth occurred in the strongly acid and the highly calcareous soils.     

Fitness and evolution in clonal plants: the impact of clonal growth

Seeds have often been emphasized in estimates of plant fitness because they are the units that carry genes to the next generation, disperse, and found new populations. We contend that clonal growth also needs to be considered when estimating fitness in clonal plants, regardless of whether fitness is measured from a genet or ramet perspective. Clonal growth affects genet fitness through both genet persistence and seed production. It affects ramet fitness through new ramet production, because both seeds and clonal propagants are considered offspring. The differential production of clonal propagants will contribute to fitness differences among individuals which may result in population-level changes in allele frequencies (i.e. microevolution). We describe a form of selection unique to clonal organisms, genotypic selection, that can result in evolution. Genotypic selection occurs when genotypically based traits are associated with differences in the rate of ramet production. It can lead to evolutionary change in quantitative trait means both directly and indirectly. It leads directly to change in the ramet population by increasing the proportion of ramets with more advantageous trait values. From the genet perspective, it leads indirectly to evolution within and among populations whenever significant portions of the genetic effect on a trait are inherited through seed. We argue that under most conditions, clonal growth will play a major role in the microevolution of clonal plants.     

Monosodium glutamate restricts the adipogenic potential of 3T3‐L1 preadipocytes through mitotic clonal expansion

Recent epidemiologic studies pointed out a significant correlation between dietary monosodium glutamate (MSG) and increased body mass index. Corroborating evidences came from animal studies depicting a clear association between dietary MSG intake and increased abdominal fat, dyslipidemia, adipocyte hypertrophy, and total body weight gain. Taken together with the inferred absence of conspicuous hypothalamic neuropathies the hallmark of disease etiopathogenesis in MSG‐obese animals, these animal studies with dietary MSG strongly argue for the presence of an alternative non‐neuronal route for MSG to mediate its adipose tissue‐specific phenotype and body weight gain. On the basis of this hypothesis, we investigated the direct effect of physiologically relevant low (100 µM), moderate (250 µM), and high dosages (2.5 and 25 mM) of MSG on distinct phases of adipocyte differentiation. MSG‐dependent changes in cell proliferation and lipid accumulation were analyzed by cell proliferation assays, flow cytometry, and biochemical methods, respectively. Physiologically relevant high dosages MSG demonstrated a significant potential in reducing MCE and thereof adipogenic capacity of preadipocytes in a dose‐dependent manner by restricting the availability of critical mitogenic proteins, CCAAT/enhancer‐binding protein β (CEBPβ), and the mitotic cyclin B. Our findings warrant further investigations to unravel the effect of long‐term dietary MSG intake on capacity of preadipocytes in different fat depots to undergo mitotic clonal expansion and hyperplasia in rodent models and human subjects, respectively.     

Synaptic connections between sensory afferents and the common inhibitory motoneuron in crayfish

The sensory inputs to the common inhibitory motoneuron that innervates every leg muscle of the crayfish Procambarus clarkii (Girard) were analyzed by performing intracellular recordings from its neurite within the neuropil of the 5th thoracic ganglion. Two types of sensory inputs involved in locomotion were studied, those from a movement coding proprioceptor (the coxobasal chordotonal organ) and those from sensory neu rons coding contact forces exerted at the tip of the leg on the substrate (the dactyl sensory afferents). Sinusoidal movements applied to the chordotonal organ strand induced a stable biphasic response in the common inhibitory motoneuron that consisted of bursts of spikes during release and stretch of the strand, corresponding to raising and lowering of the leg, respectively. Using ramp movements imposed on the chordotonal strand, we demonstrated that only movement-coding chordotonal afferents produce excitatory post-synaptic potentials in the common inhibitory motoneuron; these connections are monosynaptic. Mechanical or electrical stimulation of the dactyl sensory afferents resulted in an increase in the tonic discharge of the common inhibitory motoneuron through polysynaptic excitatory pathways. These two types of sensory cues reinforce the central command of the common inhibitory motoneuron and contribute to enhancing its activity during leg movements, and thus facilitate the relaxation of tonic muscle fibres during locomotion.Abbreviations ADR anterior distal root - A Lev anterior levator nerve - CB coxo-basipodite joint - CBCO coxo-basal chordotonal organ - CI common inhibitory motoneuron - Dep depressor nerve - DSA dactyl sensory afferents - EPSP excitatory post-synaptic potential - IN interneuron - MN motoneuron - PDR posterior distal root - P Lev posterior levator nerve - Pro promotor nerve - Rem remotor nerve     

PPARgamma1 synthesis and adipogenesis in C3H10T1/2 cells depends on S-phase progression, but does not require mitotic clonal expansion

Adipogenesis is typically stimulated in mouse embryo fibroblast (MEF) lines by a standard hormonal combination of insulin (I), dexamethasone (D), and methylisobutylxanthine (M), administered with a fresh serum renewal. In C3H10T1/2 (10T1/2) cells, peroxisome proliferator-activated receptor gamma1 (PPARgamma1) expression, an early phase key adipogenic regulator, is optimal after 36 h of IDM stimulation. Although previous studies provide evidence that mitotic clonal expansion of 3T3-L1 cells is essential for adipogenesis, we show, here, that 10T1/2 cells do not require mitotic clonal expansion, but depend on cell cycle progression through S-phase to commit to adipocyte differentiation. Exclusion of two major mitogenic stimuli (DM without insulin and fresh serum renewal) from standard IDM protocol removed mitotic clonal expansion, but sustained equivalent PPARgamma1 synthesis and lipogenesis. Different S-phase inhibitors (aphidicolin, hydroxyurea, l-mimosine, and roscovitin) each arrested cells in S-phase, under hormonal stimulation, and completely blocked PPARgamma1 synthesis and lipogenesis. However, G2/M inhibitors effected G2/M accumulation of IDM stimulated cells and prevented mitosis, but fully sustained PPARgamma1 synthesis and lipogenesis. DM stimulation with or without fresh serum renewal elevated DNA synthesis in a proportion of cells (measured by BrdU labeling) and accumulation of cell cycle progression in G2/M-phase without complete mitosis. By contrast, standard IDM treatments with fresh serum renewal caused elevated DNA synthesis and mitotic clonal expansion while achieved equivalent level of adipogenesis. At most, one-half of the 10T1/2 mixed cell population differentiated to mature adipocytes, even when clonally isolated. PPARgamma was exclusively expressed in the cells that contained lipid droplets. IDM stimulated comparable PPARgamma1 synthesis and lipogenesis in isolated cells at low cell density (LD) culture, but in about half of the cells and with sensitivity to G1/S, but not G2/M inhibitors. Importantly, growth arrest occurred in all differentiating cells, while continuous mitotic clonal expansion occurred in non-differentiating cells. Irrespective of confluence level, 10T1/2 cells differentiate after progression through S-phase, where adipogenic commitment induced by IDM stimulation is a prerequisite for PPARgamma synthesis and subsequent adipocyte differentiation.     

Pre-existing Functional Heterogeneity of Tumorigenic Compartment as the Origin of Chemoresistance in Pancreatic Tumors

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Target muscles and sensory afferents do not influence steroid-regulated,segment-specific death of identified motoneurons in Manduca sexta

Programmed cell death plays a critical role in sculpting the nervous system during embryonic development. In holometabolous insects, cell death also plays an important role in the reorganization of the nervous system during metamorphosis. In Manduca sexta, cell death and the factors that regulate it can be studied at the level of individually identified neurons. The accessory planta retractor (APR) motoneurons undergo segment-specific death during the larval-pupal transformation. APRs in abdominal segments 1, 5, and 6 die at pupation; those in abdominal segments 2, 3, and 4 survive until adulthood. Juvenile hormone and ecdysteroids regulate the metamorphic restructuring of the nervous system, but the factors that determine which APRs will live and which will die are not known. The present study assessed the possible importance of cell-cell interactions in determining APR survival at pupation by removing APR's target muscle or mechanosensory input early in the final larval instar, prior to the hormonal cues that trigger the larval-pupal transformation. The motoneurons showed their normal, segment-specific pattern of death in nearly all cases. These results suggest that target muscles and sensory input play little or no role in determining the segment-specific pattern of APR survival at pupation. © 1996 John Wiley & Sons, Inc.     

Synthesis and acrosin inhibitory activities of 5-phenyl-1H-pyrazole-3-carboxylic acid amide derivatives

A series of novel 5-phenyl-1H-pyrazole-3-carboxylic acid amide derivatives were designed, synthesized, and their acrosin inhibitory activities in vitro were evaluated. The results of the acrosin inhibitory activity showed that all target compounds were more potent than control TLCK. Compounds AQ-A1, AQ-D3, AQ-D4, AQ-E4 and AQ-E5 exhibited stronger acrosin inhibitory activities than control ISO-1. Especially, compound AQ-E5 displayed the most potent acrosin inhibitory activity in all the compounds, with an IC₅₀ of 0.01 μmol/mL. This study provided a new structural class for the development of novel acrosin inhibitory agents.     

Characterization and applications of lymphocytic clonal growth factor in human plasma

Human plasma was found to contain a macromolecular protein which can grow even a single cell of human lymphocytic cell lines (B-lymphoblastoid cell line HO-323-3 and T-lymphoblastoid cell line CCRF-CEM) and human-human hybridoma clones (SH-9, SU-1 and HB4C5) in a dish, but it has no effect on the growth of epithelial cell lines (lung cancer cell lines PC-8, QG-56 and QG-90). The proliferating activity for lymphocytic cell lines was gradually decreased at 4 or -20°C and dramatically decreased by heating at more than 60°C for 15 min. From human plasma, active fractions were purified by a successive application of Ca²⁺ treatment, ammonium sulfate fractionation, DEAE-5PW column chromatography (FPLC) at pH 7.6. These active fractions were divided into at least three proteins by DEAE-5PW chromatography at pH 8.5 and chromatofocusing. These purified factors, named lymphocytic clonal growth factors (LCGFs), had similar molecular weights of about 600 K and each factor consisted of a 180 K and two 210 K subunits associated with hydrogen bondings. By the addition of 5 g/ml of each factor into culture media, incidences of human-human hybridomas and cloning efficiencies of the hybridomas increased several-fold.     

Integrins stimulate phosphorylation of neurofilament NF-M subunit KSP repeats through activation of extracellular regulated-kinases (Erk1/Erk2) in cultured motoneurons and transfected NIH 3T3 cells

Integrin-mediated interactions of cells with components of the extracellular matrix (ECM) regulate cell survival, cell proliferation, cell differentiation and cell migration through activation of multiple intracellular signal transduction pathways. In this study, we have demonstrated that integrin-matrix interactions promote KSP tail-domain phosphorylation of neurofilament medium molecular weight subunits (NF-M) in cultured rat spinal cord motoneurons and NF-M transfected NIH 3T3 cells. We found that laminin and fibronectin induce NF-M tail-domain phosphorylation in motoneurons and NIH 3T3 cells transfected with NF-M, respectively. This phosphorylation was selectively inhibited by PD98059, a specific MEK1 inhibitor. This suggests that laminin and fibronectin-induced MEK1 activation and the downstream targets Erk1 and Erk2 are involved in NF-M KSP tail-domain phosphorylation. This pathway appears to represent one of the mechanisms whereby integrin-extracellular matrix interactions are involved in phosphorylation of the NF-M KSP tail domain.     

Population-biomass dynamics and the absence of - 3/2 self-thinning in the clonal weed Salvinia molesta

Abstract In the field, the population density (n) of crowded, living ramets of Salvinia molesta ranged from 2500 m ^?2 in nutrient-poor water to more than 30 000 m^?2 in nutrient-rich water. Biomass of living shoots (B) in some localities exceeded 600 gm^?2 dry weight (150 tonnes ha^?1 fresh weight) and shoots plus roots of living and floating dead material exceeded 1600 gm^?2 dry weight (400 tonnes ha^?1 fresh weight). The ultimate limit B= 10⁵n^0.5 suggested by previous authors was not exceeded. The highest n and smallest ramets occurred in nutrient-rich water and B was a linear function of n. Field experiments confirmed no effect of n, but a strong effect of nutrient availability, on ramet weight. In a glasshouse experiment, ramet populations did not ‘self-thin’ along the log log B-n trajectory of slope -0.5, which has been suggested for aclonal plants, but followed trajectories having slopes closer to +1.0 before halting at the ambient B-n limit. Nutrient concentrations in the plants increased during the experiment, causing ramet size to decrease and slopes of log log B-n trajectories to depart from +1.0 by amounts which reflected the degree to which nutrient concentration had changed. Under constant conditions, mean ramet size is expected to remain constant and log log B-n trajectories to travel in a straight line of slope +1.0 to the ambient B-n limit. This behaviour of salvinia, whose ramets consist of a single structural module, is contrasted with that expected of clonal plants whose ramets are made up of multiple structural modules. A logistic model explained the increases in n and biomass of living and dead ramets when ramets were assumed to have constant longevity, constant time to decay, and when both the B-n limit and size of ramets were dependent on nitrogen content of the plant. There was no indication that physiological integration within phenets halted production of new ramets when carrying capacity was reached and new ramets continued to be produced on top of older ramets. Rates of ramet mortality were equal to, and dependent on, rates of ramet natality.     

河北省东亚飞蝗发生动态及未来灾变趋势分析

80年代以来 ,尤其进入 90年代 ,由于受异常气候、农业生态及人为因素的影响 ,河北省东亚飞蝗Locustamigratoriamanilensis (Meyen)出现了暴发频次增加、发生期提前、秋蝗发生加重、潜在和隐伏蝗区突发等特点。作者分析了 5 0年来影响河北省东亚飞蝗发生动态的 5种因素 :气象因素、生态因素、湖库水位因素、河泛流量因素、人为因素等。并对河北省东亚飞蝗未来灾变趋势做了展望。     

Origin of clonal diversity in triploid parthenogenetic Trichoniscus pusillus pusillus (Isopoda,Crustacea) based upon allozyme and nucleotide sequence data

Variation in PGM (phosphoglucomutase) and MDH (malate dehydrogenase) allozymes and in mitochondrial and nuclear (ribosomal) DNA gives evidence of at least three independent origins of triploid Trichoniscus pusillus pusillus. Much of the genetic variation found may reflect variation within the parental diploid population(s), but it is argued that some of the variation in PGM allozymes have accumulated within the parthenogenetic lines. Based upon the variation at this locus, 15 genetically distinct clones are distinguished.     

Importance of clonal plants and plant species diversity in the Northeast China Transect

In plant communities, the internal (genet-level) control mechanisms on a spatio-temporal scale of clonal plants impose strong constraints on spatial pattern as well as on competitive relations and, thus, species coexistence. Therefore, the presence of clonal species within a plant community affects spatio-temporal dynamics and plant species diversity. We examined the distribution of plants with different clonal growth forms in the Northeast China Transect (NECT) and correlated plant species diversity with the importance of clonal plants, and the importance of phalanx and guerilla clonal plants. Phalanx clonal plants were more abundant in western communities where the altitude was higher and both the soil nitrogen contents and precipitation were relatively low. Whereas guerilla clonal plants were more abundant in the middle of the NECT where the precipitation, mean annual temperature and photosynthetically active radiation were relatively high. In the relatively productive temperate typical steppe, plant species diversity was negatively correlated with the importance of phalanx clonal plants and positively correlated with the importance of guerilla clonal plants. In relatively unproductive temperate desert steppe, plant species diversity was positively correlated with the importance of both phalanx and guerilla clonal plants.     

Methoxylation of resveratrol: effects on induction of NAD(P)H quinone-oxidoreductase 1 (NQO1) activity and growth inhibitory properties

A series of methoxystilbenes (E and Z isomers) related to resveratrol were investigated for their effects on NQO1 induction in murine hepatoma cells and growth inhibitory effects on human cancer cell lines. Both activities were enhanced in compounds with methoxy groups on rings A and B of resveratrol but methoxylation of the di-meta (3,5) hydroxyl groups on ring A of resveratrol was found to be more critical for improving activity. Strikingly different structure-activity trends were observed, namely the association of E isomers with potent NQO1 induction activity and Z isomers with growth inhibitory properties. The introduction of ortho-methoxy groups on ring A greatly benefited NQO1 induction activity while meta/para methoxy groups on ring A were preferred for potent growth inhibitory effects. These results serve to highlight the contrasting effects on different activities brought about by methoxylation, which is widely employed as a structural modification approach to improve potency and bioavailability of resveratrol. It serves as a timely reminder that in the course of structural modification, a balance between optimizing desired outcomes against unwanted effects is necessary and the most potent analog need not always be the most desirable.