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101.
G. Horseman F. Huber 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1994,175(4):389-398
Intracellular recordings were made in the brain of the cricket Gryllus bimaculatus from an ascending auditory interneuron (AN1). Acoustic stimuli with calling song temporal pattern were delivered via earphones in a preparation with the acoustic trachea cut (attenuation of crossing sound > 30 dB). The input-output function of this cell was then determined by recording its responses to stimulation of the ipsilateral ear alone, of the contralateral ear alone and to stimulation of both ears simultaneously with the same or different carrier frequencies and intensities.This interneuron was excited by the ear ipsilateral to its axon and dendritic field and unresponsive to stimuli presented to the axon-contralateral ear alone. However, in binaural stimulation experiments, the response to a constant ipsilateral stimulus was progressively reduced as the intensity of a simultaneous contralateral stimulus was increased, above a threshold intensity.Tuning curves for threshold of this inhibition, determined in binaural stimulation experiments, indicated significant inhibition in the range 3–20 kHz with lowest threshold at 4–5 kHz. The inhibition was unaffected by sectioning of the contralateral circumoesophageal or neck connective, indicating that the inhibitory influence crosses the midline at the level of the prothoracic ganglion. Intracellular recordings from AN1 in the prothoracic ganglion confirmed that it was indeed neurally inhibited by inputs from the contralateral ear.Tuning curves for excitation of an omega neuron (ON1) by the ear ipsilateral to its soma and also the tuning of inhibition of ON1 by its contralateral ON1 partner, closely match the tuning of inhibition of AN1 and to a lesser extent, of AN2. This was taken as evidence that each AN1 is inhibited by the contralateral ON1. The significance of this interaction for directional hearing and phonotaxis is discussed.Abbreviations AP/CHP
action potentials per chirp
- AN1, AN2
ascending auditory interneurons 1, 2
- ON1
omega neuron 1
- ipsi
ipsilateral contra contralateral
- PTG
prothoracic ganglion loc lateral ocellar nerve
- On
optic nerve an antennal nerve
- coc
circum-oesophageal connective so sound off 相似文献
102.
We examined the dose response, time course and reversibility of the effect of methyl 2-tetradecylglycidate (McN-3716, methyl palmoxirate or MEP), an inhibitor of -oxidation of fatty acids, on incorporation of radiolabeled palmitic acid ([U-14C]PA) from plasma into brain lipids of awake rats. MEP (0.1, 1 and 10 mg/kg) or vehicle was administered intravenously from 10 min to 72 hr prior to infusion of [U-14C]PA. Two hr pretreatment with MEP (0.1 to 10 mg/kg) increased brain organic radioactivity 1.2 to 1.8 fold and decreased brain aqueous radioactivity by 1.2 to 3.0 fold when compared to control values. At 10 mg/kg, MEP significantly increased brain organic fraction from 40% in controls to 85%, 30 min to 6 hr pretreatment, and resulted in a redistribution of the radiolabeled fatty acid toward triacylglycerol. MEP changed the lipid/aqueous brain ratio of incorporated [U-14C]PA from 0.67 to 5.7. The incorporation rate coefficient, k*, was significantly increased by MEP (10 mg/kg) at 2 hr (31%), 4 hr (59%) and 6 hr (34%). All effects were reversed by 72 hr, consistent with a half-life of 2 days for carnitine palmitoyl transferase I. These results indicate that intravenous MEP may be used with [1-11C]palmitic acid for studying brain lipid metabolism in vivo by positron emission tomography, as it significantly reduces the large unincorporated aqueous fraction that would result in high background radioactivity. 相似文献
103.
104.
Millie Hughes-Fulford 《Journal of cellular biochemistry》1994,54(3):265-272
Our previous studies have implied that prostaglandins inhibit cell growth independent of cAMP. Recent reports, however, have suggested that prostaglandin arrest of the cell cycle may be mediated through protein kinase A. In this report, in order to eliminate the role of c-AMP in prostaglandin mediated cell cycle arrest, we use the-49 lymphoma variant (cyc?) cells that lack adenylate cyclase activity. We demonstrate that dimethyl prostaglandin A1 (dmPGA1) inhibits DNA synthesis and cell growth in cyc? cells. DNA synthesis is inhibited 42% by dmPGA1 (50 μM) despite the fact that this cell line lacks cellular components needed for cAMP generation. The ability to decrease DNA synthesis depends upon the specific prostaglandin structure with the most effective form possessing the α,β unsaturated ketone ring. Dimethyl PGA1 is most effective in inhibiting DNA synthesis in cyc? cells, with prostaglandins PGE1 and PGB1 being less potent inhibitors of DNA synthesis. DmPGE2 caused a significant stimulation of DNA synthesis. S-49 cyc- variant cells exposed to (30–50 μm) dmPGA1, arrested in the G1 phase of the cell cycle within 24 h. This growth arrest was reversed when the prostaglandin was removed from the cultured cells; growth resumed within hours showing that this treatment is not toxic. The S-49 cyc? cells were chosen not only for their lack of adenylate cyclase activity, but also because their cell cycle has been extensively studied and time requirements for G1, S, G2, and M phases are known. Within hours after prostaglandin removal the cells resume active DNA synthesis, and cell number doubles within 15 h suggesting rapid entry into S-phase DNA synthesis from the G1 cell cycle block. The S-49 cyc? cells are known to have a G1/S boundary through M phase transition time of 14.8 h, making the location of the prostaglandin cell cycle arrest at or very near the G1/S interface. The oncogenes, c-fos and c-myc which are normally expressed during G1 in proliferating cells have a 2–3 fold enhanced expression in prostaglandin G1 arrested cells. These data using the S-49 variants demonstrate that dmPGA1 inhibits DNA synthesis and arrests the cell cycle independent of cAMP-mediated effects. The prostaglandin arrested cells maintain the gene expression of a G1 synchronous cell which suggests a unique molecular mechanism for prostaglandin action in arresting cell growth. These properties indicate that this compound may be an effective tool to study molecular mechanisms of regulation of the cell cycle. 相似文献
105.
The relationship between synthesis and N-liked glycosylation site occupancy of recombinant human prolactin produced from C127 cells was studied with the aid of a battery of protein synthesis inhibitors. Non-lethal concentrations of sodium fluoride, gougerotin, puromycin, anisomycin, and emetine did not alter site occupancy, but low concentrations (<10g ml–1) of cycloheximide increased the fraction of secreted prolactin bearing oligosaccharide from 20% to 80% of the total. Cycloheximide is an inhibitor of the elongation step of protein synthesis. The observed increase in glycosylation site occupancy upon addition of cycloheximide is consistent with the current opinion that the initial glycosylation event occurs cotranslationally during a limited time period. Cycloheximide may extend this time period by reducing elongation rate. However, the absence of any effect from treatment with other inhibitors of elongation suggests that cycloheximide is unique in its behavior on this system.Abbreviations clp-PRL
clipped form of prolactin
- DMEM/F12
11 Dulbecco's Modified Eagle's Medium/Ham's nutrient mixture F12
- G-PRL
glycosylated (N-linked) fraction of prolaction
- NG-PRL
prolactin fraction without N-linked glycosylation
- PMSF
phenylmethylsulfonylfluoride 相似文献
106.
The degradation of dichloromethane by the pure strainHyphomicrobium GJ21 and by an enrichment culture, isolated from a continuously operating biological trickling filter system, as well as the corresponding growth rates of these organisms were investigated in several batch experiments. By fitting the experimental data to generally accepted theoretical expressions for microbial growth, the maximum growth rates were determined. The effect of NaCl was investigated at salt concentrations varying from 0 to 1000 mM. Furthermore the dichloromethane degradation was investigated separately in experiments in which a high initial biomass concentration was applied. The results show that microbial growth is strongly inhibited by increased NaCl concentrations (50% reduction of max at 200–250 mM NaCl), while a certain degree of adaptation has taken place within an operational system eliminating dichloromethane. A critical NaCl concentration for growth of 600 mM was found for the microbial culture isolated from an operational trickling filter, while a value of 375 mM was found for the pure cultureHyphomicrobium GJ21. The substrate degradation appears to be much less susceptible to inhibition by NaCl. Even at 800 mM NaCl relatively high substrate degradation rates are still observed, although this process is again dependent on the NaCl concentration. Here the substrate elimination is due to the maintenance requirements of the microorganisms. The inhibition of the dichloromethane elimination was also investigated in a laboratory scale trickling filter. The results of these experiments confirmed those obtained in the batch experiments. At NaCl concentrations exceeding 600 mM a considerable elimination of dichloromethane was still observed for during several months of operation. These observations indicate that the inhibition of microbial growth offers a significant control parameter against excessive biomass growth in biological trickling filters for waste gas treatment. 相似文献
107.
用浅麻醉的Wistar大鼠40只,以辐射热照尾作为伤害性刺激,经玻璃微电极引导尾核痛兴奋神经元(PEN)和痛抑制神经元(PIN)的放电,同时测量甩尾反射潜伏期(TFL)作为甩尾痛阈的指标。结果表明:(1)自然状态下辐射热照尾引起尾核中PEN放电频率增加和PIN放电频率减少与甩尾反射(TF)相伴行。放电变化发生在TF之前,结束在TF之后,PEN和PIN放电变化与TFL呈高度正相关。(2)辐射热照尾同时引起一侧尾核PEN放电频率增加和另一侧PIN放电频率减少,二者协同活动,并发生在TF之前,结束在TF之后。(3)侧脑室注射55μg/10μl吗啡呈镇痛作用时,尾核PEN放电频率减少和PIN放电频率增加,放电变化仍发生在TF之前,结束在TF之后。结果提示,尾核中PEN、PIN放电和TF是中枢不同水平同时对痛觉调制所产生的结果。 相似文献
108.
Intensity of bacterial flagella staining using a modified silver stain was increased by aging the mordant for one week at room temperature. The use of aged mordant increased the apparent diameters of stained flagella and resulted in a darker stain. The mordant remained stable for at least four months at room temperature. The staining protocol presented allows application to liquid or solid cultures. 相似文献
109.
ANTONIO OSUNA NIEVES RODRIGUEZ-CABEZAS FRANCISCO GAMARRO CARMEN MASCARO 《The Journal of eukaryotic microbiology》1994,41(3):231-236
ABSTRACT. We have studied the action of diphtheria toxin, modeccin and ricin on HeLa cells infected by Trypanosoma cruzi . Parasitized HeLa cells were resistant to diphtheria toxin and modeccin, whereas non-parasitized cells from the same cultures and control cultures showed cytopathological alterations. Protein synthesis, assayed by the incorporation of labelled methionine, diminished in toxin-treated control cultures but remained unaltered in the infected ones, compared to synthesis by untreated infected cells. Ricin, on the other hand, is a toxin that enters the cytoplasm by endocytosis. It has greater cytopathological effects in parasitized cells than in non-parasitized ones from the same cultures or uninfected control cells. Protein synthesis was inhibited in infected cultures treated with ricin. 相似文献
110.
Richard D. Griner Rick G. Schnellmann 《In vitro cellular & developmental biology. Animal》1994,30(1):30-34
Summary We have previously shown that shaking the culture plates (SHAKE) of rabbit renal proximal tubule cells (RPTC) to maintain
adequate aeration increased aerobic metabolism and decreased the induction of glycolysis compared to RPTC cultured under standard
conditions (STILL). However, glycolysis in SHAKE RPTC remained elevated compared to glycolysis in proximal tubules in vivo.
In the present study the contribution of culture medium sugar composition and concentration to glycolytic metabolism was assessed
in RPTC. SHAKE and STILL RPTC cultured in 5 mM glucose contained lactate levels equivalent to the respective SHAKE and STILL RPTC cultured in standard culture medium which
contains 17.5 mM glucose. Similarly, the activity of lactate dehydrogenase was unchanged by lowering the medium glucose concentration. Substituting
5 mM galactose for 5 mM glucose in the culture medium significantly reduced the lactate content of both SHAKE and STILL RPTC but had no effect on
lactate dehydrogenase activity. Cell growth was equivalent under all culture conditions. Sensitivity to mitochondrial inhibition
was determined for each culture condition by measuring cell death after exposure to the respiratory inhibitor antimycin A.
The results showed a hierarchy of sensitivity to antimycin A (5 mM galactose SHAKE >5 mM glucose SHAKE >17.5 mM glucose SHAKE = 17.5 mM glucose STILL), which was generally inversely correlated with the level of glycolysis as measured by lactate content (17.5
mM glucose STILL >17.5 mM glucose SHAKE = 5 mM glucose SHAKE >5 mM galactose SHAKE). 相似文献