SEARCH · PubMed Health

Results for “Microinjection”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 757 records · Page 42Linked to original sources

PubMed1996

Naloxone partial reversal of the antinociception produced by dipyrone microinjected into the periaqueductal gray of rats. Possible involvement of medullary off- and on-cells.

Medullary off- and on-cells have been proposed to inhibit and facilitate, respectively, nociceptive transmission. Upon heating the tail in lightly anesthetized rats, the tail flick (TF) reflex occurs only after off-cells decrease and on-cells increase their activity. Dipyrone (DIP) microinjection (100 micrograms/0.5 microliter) into the periaqueductal gray (PAG) caused retardation in the off-cell pause, on-cell burst and corresponding TF. This effect was partly reverted by naloxone given i.v. (l mg/kg) or microinjected into PAG (5 micrograms/0.5 microliter). These results suggest that endogenous opioids are partly responsible for the central antinociceptive action of DIP, and that such action involves medullary off- and on-cells.

Animals↗

PubMed1996

Brainstem mediates diazepam enhancement of palatability and feeding: microinjections into fourth ventricle versus lateral ventricle.

The hypothesis that benzodiazepine-induced hyperphagia is due to a specific enhancement of the palatability of foods has been supported by previous 'taste reactivity' studies of affective (hedonic and aversive) reactions to taste palatability. Diazepam and chlordiazepoxide enhance hedonic reactions of rats (rhythmic tongue protrusions, etc.) to sweet tastes in a receptor-specific fashion. A role for brainstem circuits has been indicated by a previous demonstration of the persistence of the taste reactivity enhancement by diazepam after midbrain decerebration. The present study examined whether benzodiazepine brainstem receptors are the chief substrates for palatability enhancement even in intact brains. We compared the effectiveness of benzodiazepine microinjections to elicit feeding and enhance hedonic reactions when delivered into either the lateral ventricle (forebrain) or the fourth ventricle (brainstem) of rats. The results show diazepam is reliably more effective at eliciting feeding and enhancing positive hedonic reactions to oral sucrose when microinjections are made in the fourth ventricle than in the lateral ventricle. We conclude that brainstem neural systems containing benzodiazepine-GABA receptors are likely to be the chief substrates for benzodiazepine-induced palatability enhancement.

Animals↗

PubMed1982

Local electrographic effects of leu-enkephalin microinjections into the brain.

Microinjections of Leu-enkephalin were made in dorsal hippocampus, caudate nucleus, amygdala, nucleus accumbens and parietal cortex in rats. The effects of enkephalin on the local electrical activity recorded from the area of the microinjection are described. Depression effects (attenuation of amplitudes and slowing) were recorded in caudate nucleus, nucleus accumbens, amygdala and parietal cortex, but not in hippocampus. Activation and epileptiform effects (spikes, seizures) were recorded from all structures studied.

Animals↗

PubMed1979

Analgesia produced by microinjection of baclofen and morphine at brain stem sites.

Microinjection of either baclofen (1.5 microgram) or morphine (2.5 microgram), in equimolar doses (14 mM), at sites located in the caudal periaqueductal gray (PAG) resulted in a delay in tail flick latency (analgesia). The relative analgesic potency of baclofen among caudal PAG sites, however, did not correlate with that of morphine. Application of either drug into the caudal aspect of the cerebral aqueduct also produced analgesia, but neither agent caused analgesia when applied at PAG sites rostral to the interaural line. Baclofen also produced analgesia when microinjected in the lower brain stem at sites lateral to the midline in or near the nucleus gigantocellularis, but did not produce analgesia when applied on the midline at sites located within or near the raphe magnus. Conversely, morphine produced analgesia when applied locally at midline sites but not at sites located lateral to the midline. These data suggest that the analgesia produced by systemic administration of baclofen and morphine involves activation of different neuronal substrates.

Analgesics↗

PubMed1985

Behavioral effects of microinjections of SR 95103, a new GABA-A antagonist, into the medial hypothalamus or the mesencephalic central gray.

The behavioral effects of unilateral microinjections of SR 95103, a new GABA-A receptor antagonist, into periventricular structures were studied. When injected into the medial hypothalamus (MH) or into the dorsal part of the mesencephalic central gray (CG), SR 95103 produced a dose-dependent behavioral activation together with jumps. However, the characteristics of this behavioral activation differed according to whether SR 95103 was injected into the MH or into the CG. The behavioral activation was found to be attenuated by pretreatment with THIP, a GABA receptor agonist. When injected into the CG or into the deep layers of the superior colliculus, SR 95103 proved to affect the rat's reactivity to tactile stimuli as evidenced by ipsilateral 'neglect' combined with contralateral hyperreactivity expressed as withdrawal reactions and jumping. Similar results were obtained following microinjections of bicuculline methiodide at the same sites. These data confirm that in both the MH and the CG, GABA-A receptors are involved in the neural control of the generation and/or expression of aversive effects. The data further suggest that at the level of the CG and the deep layers of the superior colliculus, GABA is also involved in the gating of sensory information towards the substrate underlying the generation of such aversive effects.

Animals↗

PubMed1983

Transformation of L cells with virus thymidine kinase genes introduced by red cell-mediated microinjection.

Fusion of red cell ghosts containing foreign materials with cells results in the introduction of the materials into the cells (red cell-mediated microinjection). Until now, 'two-step dialysis' has mainly been used for trapping proteins in the ghosts. Large-sized materials such as DNA, however, are rarely trapped in the ghosts, since the holes in the red cell membrane caused by osmotic shock are too small for such materials to pass through. In this study, we improved the trapping technique. Some of the Hind III fragments of lambda phage DNA as well as proteins could be trapped in the ghosts when the mixture of these materials and red cells were frozen at -80 degrees C for a short period followed by quick thawing. Red cell-mediated microinjection using ghosts containing plasmid pBR322 linked with a Herpes simplex viral thymidine kinase (tk) gene brought about transformation of tk-defective L cells, the efficiency of transformation was 1 out of 20 000-60 000 cells fused with the ghosts.

Animals↗

PubMed1984

Microinjection studies of protein transit across the nuclear envelope of human cells.

Proteins of various molecular weights were conjugated with rhodamine and microinjected into the cytoplasm or nucleus of HeLa cells. The injected proteins were then localized within the cells at various times thereafter with fluorescence microscopy. Proteins below approx. 60 kD rapidly crossed the HeLa nuclear envelope. Some larger proteins also were able to pass into or out of the nucleus, while others were unable to do so, indicating the selective permeability of the HeLa nuclear envelope to large proteins. The nuclear protein HMG17 accumulated within the nucleus shortly after cytoplasmic microinjection.

Biological Transport↗

PubMed1986

Morphology of endoplasmic reticulum and Golgi elements following microinjection of rat liver microsomes into Xenopus laevis oocyte cytoplasm.

Fragments of rough endoplasmic reticulum and Golgi complex purified from rat liver homogenates were injected into Xenopus oocytes and the sites of microinjection analysed by electron microscopy at different times post-injection. The in vivo incubated fragments were located by their proximity to a microinjection vacuole, and identified by their association with specific morphological markers (peroxisomal cores associated with rough microsomes and lipoprotein particles with Golgi derivatives). Typical endoplasmic reticulum microsomes disappeared with time post-injection and seemed to be replaced by flattened cisternae of endoplasmic reticulum. Golgi fragments as defined by their content of lipoprotein particles became modified. Many were found associated with coated vesicles and some displayed membrane-coated regions. Furthermore lipoprotein particles were observed as integral components of Golgi stacks and were found within dilated rims in direct continuity with fenestrated Golgi saccules. The results suggest that the injected organelle fragments underwent transformation in vivo as a consequence of reconstitution.

Animals↗

PubMed1988

Single cell assay with an automated capillary microinjection system.

An automated capillary microinjection system with computer-controlled positioning of the cells and of the capillary, and its applications and advantages, is described. The system is easy in handling and manipulation. About 1500 injections are possible in 1 h, with high reproducibility. In cytoplasmic and nuclear injections more than 90 and 85% of the cells are successfully injected. Using FITC-dextran at a concentration of 0.5% as a fluorescently labeled coinjection marker, 99% of the cells can be retrieved in culture medium even 48 h after injection. The coordinates of the cells are stored in the computer and accuracy in statistical evaluation of experiments is improved in comparison to the manual techniques. Methods for preparation and handling of glass capillaries were developed resulting in reproducible form and significantly reduced clogging rate. The improved characteristics offered by this system are demonstrated in studies leading to the confirmation of existence of an mRNA inhibiting DNA synthesis in cells. Functional screening by cell injections of cDNA libraries and of size-fractionated mRNA molecules can be performed efficiently with the automated microinjection system.

Autoradiography↗

PubMed1990

Fusion-mediated microinjection of liposome-enclosed DNA into cultured cells with the aid of influenza virus glycoproteins.

Influenza viruses were able to mediate fusion of DNA-loaded liposomes with living cultured cells such as monkey COS-7 cells. This was inferred from the appearance of CAT activity in recipient cells incubated with the combination of influenza viruses and liposomes loaded with the plasmid pSV2CAT. Influenza virions were found to be as efficient as intact Sendai virions in mediating microinjection of foreign DNA into living cells. Also, reconstituted envelopes bearing either influenza glycoproteins or the combination of Sendai and influenza glycoproteins were highly efficient in promoting fusion of loaded liposomes with recipient cells. Introduction of DNA into cultured cells required the presence of an active influenza fusion protein; namely, an active HA glycoprotein. Very little or no CAT activity was observed in cells incubated with loaded liposomes and unfusogenic influenza viruses. The virus-induced fusion event probably occurs within intracellular organelles such as endosomes following receptor-mediated endocytosis of virus-liposome complexes. This is due to the fact that the viral fusion glycoprotein is activated only at acidic pH values such as those which characterize the intraendosomal environment. Results of the present work demonstrate for the first time microinjection of foreign DNA via fusion with membranes of intracellular organelles. The potential of the present system to serve as a biological carrier for in vivo use is discussed.

Animals↗

PubMed1991

Effective intracellular inhibition of the cAMP-dependent protein kinase by microinjection of a modified form of the specific inhibitor peptide PKi in living fibroblasts.

In order to obtain a peptide retaining its biological activity following microinjection into living cells, we have modified a synthetic peptide [PKi(m)(6-24)], derived from the specific inhibitor protein of the cAMP-dependent protein kinase (A-kinase) in two ways: (1) substitution of the arginine at position 18 for a D-arginine; (2) blockade of the side chain on the C-terminal aspartic acid by a cyclohexyl ester group. In an in vitro assay, PKi(m) has retained a specific inhibitory activity against A-kinase as assessed against six other kinases, with similar efficiency to that of the unmodified PKi(5-24) peptide. Microinjection of PKi(m) into living fibroblasts reveals its capacity to prevent the changes in cell morphology and cytoskeleton induced by drugs which activate endogenous A-kinase, whereas the original PKi peptide failed to do so. This inhibition of A-kinase in vivo by PKi(m) lasts between 4 and 6 h after injection. In light of its effective half-life, this modified peptide opens a route for the use of biologically active peptides in vivo, an approach which has been hampered until now by the exceedingly short half-life of peptides inside living cells. By providing a direct means of inhibiting A-kinase activity for sufficiently long periods to observe effects on cellular functions in living cells, PKi(m) represents a powerful tool in studying the potential role of cAMP-dependent phosphorylation in vivo.

Amino Acid Sequence↗

PubMed1991

Characterization of PC2, a mammalian Kex2 homologue, following expression of the cDNA in microinjected Xenopus oocytes.

A human insulinoma cDNA (PC2) that encodes a protein homologous to the Kex2/subtilisin-like proteinases has recently been described [1990, J. Biol. Chem. 265, 2997-3000]. In order to characterise the associated proteinase activity, mRNA encoding PC2 was synthesised in vitro and microinjected into Xenopus oocytes. The proteinase activity released into the media from oocytes microinjected with PC2 mRNA was assayed using small peptide fluorogenic substrates. Boc.Gln.Arg.Arg aminomethyl coumarin was hydrolysed in a Ca(2+)-dependent manner, but substrate analogues bearing a single basic aminoacid were not. The substrate specificity, inhibitor profile, and pH optimum of 5.5 were compatible with an involvement of PC2 in prohormone processing in mammalian cells.

Animals↗

PubMed1995

An SH3 domain is required for the mitogenic activity of microinjected phospholipase C-gamma 1.

Phospholipase activity is elevated in dividing cells. In response to growth factor stimulation, phospholipase C-gamma (PLC-gamma) binds to activated tyrosine kinase receptors via SH2 binding domains, resulting in phosphorylation of PLC-gamma and activation of its enzyme activity. These observations suggest that PLC-gamma participates in the signal transduction pathway employed by growth factors to promote mitogenesis. Consistent with this hypothesis, microinjection of purified bovine PLC-gamma into quiescent fibroblasts has been previously reported to initiate a mitogenic response [Smith et al. (1989) Proc. Natl. Acad. Sci. 86, 3659]. We have reproduced this result using recombinant rat PLC-gamma protein. Surprisingly, however, a catalytically inactive mutant of PLC-gamma, H335Q, also elicited a full mitogenic response. The capacity to induce mitogenesis by microinjection of PLC-gamma was mapped to the 'Z' domain of the protein, which contains PLC-gamma's SH2 and SH3 motifs. Inactivation of the phosphorylated tyrosine binding properties of both SH2 domains had no effect on the mitogenic activity of the Z-domain peptide. However, deletion of the SH3 domain resulted in a complete loss of activity. These results suggest that PLC-gamma's mitogenic properties do not require the enzyme's phospholipase activity, but are instead mediated by a novel pathway for mitogenic stimulation which is dependent upon an intact SH3 domain.

3T3 Cells↗

PubMed1996

SV40 T1-mRNA trans-splicing and translation requires that the in vitro synthesized cRNA is capped before microinjection.

The purpose of this investigation was to study the effect on cap structure for trans-splicing in mammalian cells. The early SV40 Bst/Bam pre-mRNA (cRNA) was synthesized in vitro in both capped (cap-Bst/Bam-cRNA) and non-capped (Bst/Bam-cRNA) versions and microinjected into the nuclei of TC7 cells. Trans-splicing was monitored by immunofluorescence staining (T1-antigen) and by RT-PCR analysis. Cap-Bst/Bam-cRNA was trans-spliced with high efficiency, but not the Bst/Bam-cRNA molecules. Northern blot analysis revealed that both the capped and uncapped cRNA molecules had similar stability in the microinjected cells. The coinjected m7G(5')ppp(5')G cap analog did not inhibit the trans-splicing reaction in vivo and did not prevent nuclear export of the mRNA.

Animals↗

PubMed1995

Pancreatic polypeptide microinjection into the dorsal motor nucleus inhibits pancreatic secretion in rats.

BACKGROUND/AIMS: Pancreatic polypeptide (PP), a hormone released from the pancreas, inhibits pancreatic secretion in vivo but not in vitro, suggesting that the inhibitory action of PP on pancreatic secretion is indirect. Circulating PP in physiological concentrations binds to specific receptors in the dorsal vagal complex in the brainstem. Therefore, the hypothesis of this study was that PP acts centrally and inhibits pancreatic secretion by modulating vagal tone. METHODS: The effects of microinjection of PP into the dorsal motor nucleus on 2-deoxy-D-glucose-stimulated and cholecystokinin octapeptide (CCK-8)-stimulated pancreatic secretion were examined in urethane-anesthetized rats. RESULTS: Microinjection of PP to the dorsal motor nucleus but not brainstem sites outside it inhibited 2-deoxy-D-glucose-stimulated pancreatic flow and protein output. CCK-8-stimulated pancreatic protein output was inhibited by PP in the dorsal motor nucleus in dose-dependent and site-specific manners. The inhibitory effect of PP on CCK-8-stimulated protein output was eliminated by vagotomy. CONCLUSIONS: The results suggest that PP acts in the dorsal motor nucleus to modulate vagal tone on the pancreas, thereby inhibiting pancreatic secretion. This study shows for the first time that the dorsal motor nucleus is involved in central feedback inhibition of the exocrine pancreas.

Analysis of Variance↗

PubMed1983

Morphine microinjections into periaqueductal grey matter of the rat: effects on dorsal horn neuronal responses to C-fibre activity and diffuse noxious inhibitory controls.

Recording were made for dorsal horn convergent neurones with hindpaw receptive fields. Response to C-fibre activation was conditioned by noxious heat (52 degrees C) applied to the tail, this resulting in profound inhibition (Diffuse Noxious Inhibitory Controls - DNIC). The microinjection of 5 micrograms morphine into the medioventral PAG, including the n. raphé dorsalis, consistently reduced DNIC without affecting the unconditioned C-fibre responses; more lateral injections had no clear effects. Including a further study in which 20 micrograms morphine was microinjected within various PAG sites, C-fibre responses were found to be unaltered (21/51) enhanced (16/51) or reduced (4/51) with no consistent anatomical basis. The results imply that supraspinal morphine can reduce descending inhibitions and this may contribute to the consequent analgesia.

Animals↗

PubMed1989

Microinjection of cholecystokinin into the medial preoptic nucleus facilitates lordosis behavior in the female rat.

We examined the effect of cholecystokinin (CCK) on lordosis behavior when administered into the medial preoptic area or the nucleus accumbens (NAcc) of ovariectomized estrogen-primed female rats. The frequency of lordotic responses was measured subsequent to unilateral microinjections of sulphated octapeptide CCK (sCCK-8) into the medial preoptic nucleus (MPN) or the NAcc. In the first experiment, three doses of sCCK-8 (1, 5, and 50 ng) microinjected into the MPN, and 50 ng injected into the NAcc produced a marked facilitation of lordosis. In a separate experiment, unilateral injections of an undiluted sCCK-8 antiserum into the MPN produced significant reduction in lordosis behavior in highly receptive females when compared with a normal rabbit serum injected control group. The results of the present study indicate that the CCK innervation of the MPN is involved in the neural regulation of lordosis behavior in the female rat.

Animals↗

PubMed1993

Microinjection of galanin into the medial preoptic nucleus facilitates copulatory behavior in the male rat.

The medial preoptic area (MPOA) is an important region for masculine sexual behavior. Because galanin (GAL) immunoreactive cells within the MPOA are affected by the gonadal steroid environment and GAL binding is apparent, GAL was microinjected site specifically in 0, 10, 50, 100, and 500 ng doses in order to determine effects on copulatory behavior. Unilateral microinjection of GAL within the medial preoptic nucleus facilitated copulatory behavior in a dose-responsive fashion, evidenced by an increase in the percentage of males that displayed sexual behaviors and a decrease in mount and intromission latencies. These effects required the presence of gonadal steroids, and were not due to general arousal as measured in open field testing. The techniques of survival analysis were used to display data and for statistical analysis of intromission and mount latencies; these approaches revealed significant effects that were not evident with more commonly used procedures. The results support the suggestion that sexually dimorphic galaninergic cell groups within the MPOA are involved in gonadal steroid-induced masculine sexual behavior.

Animals↗