Bradykinin Stimulates Phosphoinositide Hydrolysis and Mobilization of Arachidonic Acid in Dorsal Root Ganglion Neurons

Cultures of fetal rat dorsal root ganglion neurons (7 days in culture) were prelabeled with myo-[3H]inositol or [3H]arachidonic acid for 24 h and stimulated with 10 microM bradykinin for time intervals of 5-300 s. The incubation was terminated by addition of 5% perchloric acid to extract inositol phosphates or organic solvent to extract lipids. Inositol phosphates were resolved by anion-exchange HPLC; lipids were resolved by TLC. Bradykinin stimulation resulted in a 10-fold increased accumulation of inositol 1,4,5-trisphosphate (IP3) and inositol bisphosphate (IP2) (fivefold) by 5 s. The increase in IP3 was transient (half maximal by 1 min), whereas stimulated IP2 levels were sustained for several minutes. Even longer term increases were observed in inositol monophosphate. Stimulation also resulted in a threefold increase in arachidonic acid which was preceded by transient increases in diacylglycerol (twofold) and arachidonoyl-monoacylglycerol (threefold). The temporal lag in the accumulation of arachidonic acid with respect to diglyceride and monoglyceride suggested the involvement of di- and monoglyceride lipases in arachidonic acid mobilization. A role for phospholipase A2 is also possible, because pretreatment of cultures with quinacrine partially blocked arachidonic acid release. Bradykinin-stimulated arachidonic acid release was decreased in the presence of calcium channel blockers nifedipine or verapamil (50 microM), or EDTA (2.5 mM). The role of calcium was verified further in that accumulation of phosphatidic acid, diacylglycerol, and arachidonic acid was maximally stimulated by treatment with the calcium ionophore A23187 (20 microM).     

Flesinoxan Dose-Dependently Reduces Extracellular 5-Hydroxytryptamine (5-HT) in Rat Median Raphe and Dorsal Hippocampus Through Activation of 5-HT1A Receptors

Abstract: The effects of systemic administration of the serotonin (5-hydroxytryptamine) 5-HT_1A receptor agonists flesinoxan and 8-hydroxy-2-(di- n -propylamino)tetralin on extracellular 5-HT were measured using microdialysis probes in both median raphe nucleus and dorsal hippocampus. Both 5-HT_1A agonists dose-dependently decreased dialysate 5-HT levels from both brain regions. The effects of flesinoxan in the median raphe (0.3 mg/kg) and dorsal hippocampus (1.0 mg/kg) could be blocked by the 5-HT_1A receptor antagonist N -[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]- N -(2-pyridyl)cyclohexane carboxamide trihydrochloride (WAY 100,635) at a dose of 0.05 mg/kg s.c. The antagonist itself had no effect at this dosage. Local perfusion of flesinoxan for 30 min through the dialysis probe into the median raphe region at concentrations of 20, 100, and 1,000 n M resulted in a significant decrease in dialysate 5-HT content from both regions. The effect of 100 n M flesinoxan could be blocked by coperfusion of 1,000 n M WAY 100,635. The data indicate that flesinoxan is a potent 5-HT_1A receptor agonist and also support the notion that somatodendritic 5-HT_1A autoreceptors regulate both terminal and somatodendritic 5-HT release.     

Predator-induced phenotypic plasticity in Daphnia pulex: uncoupling morphological defenses and life history shifts

Chemical cues from a predator Chaoborus sp. induce morphological defense (neck spine) and life history shifts (later reproduction, decreased fecundity but larger juvenile size) in the waterflea Daphnia pulex. These shifts have been interpreted either as costs of defense or as separate adaptation. In order to investigate if the life history shifts can be separated from the morphological defense, Daphnia pulex individuals were exposed to chemical cues from Chaoborus at different stages of life for variable periods. The daphnids that were exposed to Chaoborus started their reproduction later than the controls, although the differences were not statistically significant. Neck spine was induced only if daphnids were exposed to Chaoborus in an early stage of their life. Numbers of eggs produced were not affected by the different treatments, but egg mortality was higher in mothers exposed to Chaoborus. With these treatments it was possible to see neck spine induction without measurable life history changes or costs. On the other hand, irrespective of neck spine presence, the Chaoborus chemical(s) had an effect on Daphnia pulex mothers.Publication no 2159. Netherlands Institute of Ecology, Centre for LimnologyPublication no 2159. Netherlands Institute of Ecology, Centre for Limnology     

Prosaposin Facilitates Sciatic Nerve Regeneration In Vivo

Abstract: Prosaposin, a multifunctional protein, is the precursor of saposins, which activate sphingolipid hydrolases. In addition to acting as a precursor for saposins, prosaposin has been shown to rescue hippocampal CA1 neurons from lethal ischemic damage in vivo and to promote neurite extension of neuroblastoma cells in vitro. Here we show that prosaposin, when added to a collagen-filled nerve guide after sciatic nerve transection in guinea pigs, increased dramatically the number of regenerating nerve fibers within the guide. To identify the target neurons of prosaposin during peripheral nerve regeneration, we determined the degree of atrophy and chromatolysis of neurons in the spinal anterior horn and dorsal root ganglia on the prosaposin-treated and untreated side. The effect of prosaposin on large spinal neurons and small neurons of the dorsal root ganglion was more conspicuous. Subsequent immunohistochemistry demonstrated that the atrophy of cholinergic large neurons in the anterior horn is prevented to significant extent by prosaposin treatment. These findings suggest that prosaposin promotes peripheral nerve regeneration by acting on α-motor neurons in the anterior horn and on small sensory neurons in the dorsal root ganglion. The present study raises the possibility of using prosaposin as a tool for the treatment of peripheral nerve injuries.     

A role for GABAergic inhibition in electrosensory processing and common mode rejection in the dorsal nucleus of the little skate, Raja erinacea

The electrosensory primary afferents in elasmobranchs are responsive to electric potentials created by the animal's own ventilation, while the second-order neurons (AENs) which receive this afferent input in the medulla suppress responses to ventilatory potentials but retain their extreme sensitivity to electric signals in the environment. Ventilatory potentials are common mode signals in elasmobranchs and a common mode rejection mechanism is one way the AENs suppress ventilatory noise. By pressure injecting the GABA-A receptor antagonist SR95531 while extracellularly recording from AENs, we tested the hypothesis that the subtractive circuitry that selectively reduces common mode signals in AENs utilizes GABA, and that a GAB-Aergic component of the dorsal nucleus commissural pathway mediates crossed inhibition of AENs. Local application of SR95531 increased the spontaneous activity and the responsiveness of AENs to electrosensory stimuli. AEN responses to a common mode stimulus were selectively increased compared to responses to a localized stimulus due to SR95531 application. Contralateral inhibition of AENs was blocked by SR95531, indicating that GABAergic commissural cells may inhibit AENs when the contralateral side of the body is stimulated, as with common mode stimulation. We conclude that GABAergic inhibition contributes significantly to the shaping of AEN responses including common mode rejection.Abbreviations AENs ascending efferent neurons - GABA gamma-aminobutyric acid     

刺激中缝背核调制小脑间位核神经元电活动

刺激中缝背核（ｄｏｒｓａｌｒａｐｈｅｎｕｃｌｅｕｓ,ＤＲ）可以引起小脑间位核（ｉｎｔｅｒｐｏｓｅｄｎｕｃｌｅｕｓ,ＩＮ）神经元抑制,兴奋和双相（抑制－兴奋和兴奋－抑制）３种不同类型的反应,其中以抑制反应为主（７６．０％）,多数细胞的反应潜伏期〈３０ｍｓ。ＩＮ细胞的自发放电频率为５－１２０Ｈｚ,自发放电频率高的神经元群体对ＤＲ刺激的反应率却比自发放电频率低的群体低。静脉注射５－ＨＴ２／１ｃ受体阻断剂     

Evidence for a GABAergic Projection from the Dorsal Nucleus of the Lateral Lemniscus to the Inferior Colliculus

Abstract: This study attempts to determine whether the pathways from the guinea pig dorsal nucleus of the lateral lemniscus (DNLL) to the inferior colliculus (IC) use γ-aminobutyric acid (GABA) as a transmitter. Injections of kainic acid (KA) were used to destroy neurons in the left DNLL. Two to 4 days after the injection, Nissl-stained sections through the lesion site showed destruction of the DNLL neurons. The lesions varied in size; 12–100% of the DNLL neurons were destroyed on the injected side without damage to the ipsilateral IC. Two to 4 days after the injection, the electrically evoked, Ca²⁺-dependent release and high-affinity uptake of [³H]GABA were measured in dissected pieces of the left and right IC. These activities were compared with those in the IC taken from unlesioned controls and from sham controls, which received injections of saline instead of KA. Each IC was divided into a dorsal piece, which contained the dorsal cortex and dorsomedial nucleus, and a ventral piece, which contained the central and lateral nuclei. Lesions of the left DNLL depressed the release and uptake of [³H]GABA in the ventral pieces of the IC, but there was a greater depression in the ventral IC contralateral to the lesioned DNLL. There were good correlations between the percentage of neuronal loss in the left DNLL and deficits in [³H]GABA release and uptake activities in the ipsi- and contralateral ventral IC. By contrast, there was no depression of [³H]GABA release and uptake in the dorsal pieces of the IC. The localization of the deficits in release and uptake appears to match the distribution of the synaptic endings of the DNLL pathways in the IC. This correspondence associates GABA release and uptake activities with the DNLL projections to the IC and, therefore, suggests that GABA may be a transmitter of these pathways. The release and uptake of [¹⁴C]glycine was also measured to determine whether glycine might be a transmitter of the DNLL pathways to the IC. Lesions of the left DNLL failed to alter the Ca²⁺-dependent release or the uptake of [¹⁴C]glycine, suggesting that DNLL neurons are unlikely to use this compound as a transmitter.     

Cellular components of the immune barrier in the spinal meninges and dorsal root ganglia of the normal rat: immunohistochemical (MHC class II) and electron-microscopic observations

This report deals with the distribution, morphology and specific topical relationships of bone-marrow-derived cells (free cells) in the spinal meninges and dorsal root ganglia of the normal rat. The morphology of these cells has been studied by transmission and scanning electron microscopy. Cells expressing the major histocompatibility complex (MHC) class II gene product have been recognized by immunofluorescence. At the level of the transmission electron microscope, free cells are found in all layers of the meninges. Many of them display characteristic ultrastructural features of macrophages, whereas others show a highly vacuolated cytoplasm and are endowed with many processes. These elements lack a conspicuous lysosomal system and might represent dendritic cells. Scanning electron microscopy has revealed that free cells contact the cerebrospinal fluid via abundant cytoplasmic processes that cross the cell layers of the pia mater and of the arachnoid. Cells expressing the MHC class II antigen are also found in all layers of the meninges. They are particularly abundant in the layers immediately adjacent to the subarachnoid space, in the neighbourhood of dural vessels, along the spinal roots and in the dural funnels. In addition to the meninges, strong immunoreactivity for MHC class II antigen is observed in the dorsal root ganglia. The ultrastructural and immunohistochemical findings of this study suggest the existence of a well-developed system of immunological surveillance of the subarachnoid space and of the dorsal root ganglia.     

Comparative Transcriptome Analyses Reveal Genes Related to Spine Development in Cucumber (<i>Cucumis sativus</i>)

Fruit spine is an important quality trait of cucumber. To better understand the molecular basis of cucumber spine development and function, RNA-Seq was performed to identify differentially expressed genes (DEGs) in fruit spines of different development stages, namely, 8 days before anthesis (SpBA8), anthesis (SpA) and 8 days after anthesis (SpAA8). Stage-wise comparisons obtained 2,259 (SpBA8 vs. SpA), 4,551 (SpA vs. SpAA8), and 5,290 (SpBA8 vs. SpAA8) DEGs. All the DEGs were classified into eight expression clusters by trend analysis. Among these DEGs, in addition to the Mict, Tril, CsTTG1, CsMYB6, NS, and Tu genes that have been reported to regulate fruit spine formation, we found that the CsHDG11, CsSCL8, CsSPL8, CsZFP6 and CsZFP8 may also be involved in spine development in cucumber. Our study provides a theoretical basis for further research on molecular mechanisms of spine development in cucumber.     

The function of type IV collagen during Drosophila embryogenesis

A collagen gene (Dcg1) was characterized in Drosophila melanogaster and shown to encode a peptide related to vertebrate basement membrane type IV collagen chains. To study the function of type IV collagen during Drosophila development, we transformed flies with a partially truncated Dcg1 gene under the control of a heat-shock promotor. This construct induced synthesis of shortened pro- chains which associated with normal ones and thereby caused degradation of the shortened and normal pro- chains through a process called pro-collagen suicide. A large proportion of embryos expressing the transgene developed a phenotype exhibiting absence or partial retraction of the germ band with defects in nerve cord condensation and dorsal closure. Together these results indicated that, during embryogenesis, type IV collagen was an essential guiding factor for cell-matrix interactions in morphogenetic events.