Nonlinear optical spectroscopy in GaAs: Magnetic freezeout of excitons.
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Journal Article↗
Biomedical subjects
M Jiang
Publications and source records attributed to M Jiang.
Activation of serotonin1A receptors inhibits midbrain periaqueductal gray neurons of the rat.
The midbrain periaqueductal gray (PAG) is involved in a variety of functions including pain modulation, vocalization, autonomic control, fear and anxiety. This area contains serotonin receptors, particularly 5-HT1A that are known to play a role in the above functions. The goals of this study were to characterize the effects of 8-OH-DPAT, a selective 5-HT1A agonist, on the firing characteristics and membrane properties of PAG neurons. Both in vivo and in vitro preparations were used. The effects of 8-OH-DPAT on baseline activity of 91 neurons were tested in the in vivo preparation. In 50/91 cells, 8-OH-DPAT produced a decrease in the firing rate that ranged between 21 and 98% (mean +/- S.E.M. decrease of 49 +/- 1.9%). This inhibitory effect was dose dependent and could be blocked by spiperone. In 10/91 cells, 8-OH-DPAT produced an increase in the firing rate that ranged between 13 and 290%, with mean increase of 83 +/- 7.4%. The baseline firing rate of the remaining 31 cells was not affected by 8-OH-DPAT. In the PAG slice preparation, the effects of 8-OH-DPAT on synaptic and membrane properties of 17 PAG neurons were tested using whole-cell voltage clamp-recording procedures. In 14 cells, application of 8-OH-DPAT produced hyperpolarization that ranged between 6 and 21 mV, with mean of 8.4 +/- 2.0 mV. This hyperpolarization was associated with a decrease in membrane impedance that ranged between 8 and 45%, with mean decrease of 21.6 +/- 4.5%. The remaining three neurons did not respond to 8-OH-DPAT.(ABSTRACT TRUNCATED AT 250 WORDS)
8-Hydroxy-2-(di-n-propylamino)tetralin↗
Pilocarpine-induced convulsions in rats: evidence for muscarinic receptor-mediated activation of locus coeruleus and norepinephrine release in cholinolytic seizure development.
We recently reported that systemic administration of the anticholinesterase, soman, caused rapid depletion of forebrain norepinephrine (NE) in convulsive but not in nonconvulsive rats. As neurons in nucleus locus coeruleus (LC) provide the bulk of NE innervation to most of the forebrain and the sole source of NE input to the cortex and the olfactory bulb, soman-induced NE depletion was hypothesized to result from activation of LC neurons. This activation was thought to be due to inhibition of acetylcholinesterase by soman, leading to rapid, sustained accumulation of acetylcholine in LC, causing these cells to fire at a high sustained rate. Support for this hypothesis was provided by neurophysiological findings showing that: (i) Systemic administration of soman in anesthetized rats caused a sustained, fivefold increase in the mean firing rate of LC neurons and (ii) microinjections of soman directly into LC caused a similar increase in the firing rate of LC neurons. Soman-induced activation of LC occurred prior to and even in the absence of seizures. As systemic administration of the muscarinic receptor antagonist, scopolamine, rapidly and completely reversed soman-induced activation of LC, it was further hypothesized that activation of LC neurons following soman administration is due to muscarinic receptor stimulation. The rapid release of NE by cholinolytic agents, thus, may play an important role in the initiation and/or maintenance of convulsions. To further test the hypothesis that NE release in soman-intoxicated rats is due to muscarinic activation of LC, we have investigated the effects of the muscarinic receptor agonist, pilocarpine, on NE release and LC discharge. In one set of experiments, rats were injected with a periconvulsive dose of pilocarpine (300 mg/kg, ip); both convulsive and nonconvulsive rats were sacrificed between 1 and 96 h and monoamine levels in the rostral forebrain and olfactory bulb were determined by HPLC with electrochemical detection. NE levels declined substantially only in convulsive rats; forebrain NE levels in convulsive rats rapidly decreased to 50% of control levels at 1 h and to 37% of controls level between 2 and 4 h. The time course and magnitude of these changes were similar to those observed following soman administration in our previous study. Recovery of forebrain NE began at 8 h and was complete by 96 h following pilocarpine administration. Neither dopamine (DA) nor serotonin (5-HT) levels were changed in the forebrain and olfactory bulb of either convulsive or nonconvulsive rats.(ABSTRACT TRUNCATED AT 400 WORDS)
3,4-Dihydroxyphenylacetic Acid↗
Physiological influence of lateral proisocortex on the midbrain periaqueductal gray: evidence for a role of an excitatory amino acid in synaptic activation.
Recent anatomical studies in this laboratory have demonstrated that the proisocortex cortex adjacent and dorsal to the rhinal sulcus is one of the major forebrain afferent inputs to the midbrain periaqueductal gray matter in the rat. The physiological influence(s) of this projection has not been examined. The present studies investigated the responses of periaqueductal gray neurons to chemical and electrical stimulation of proisocortex in chloral hydrate-anesthetized rats. In addition, the role of glutamate as a possible transmitter in excitatory proisocortex-periaqueductal gray synaptic responses was tested. Microinjection of D,L-homocysteate into proisocortex excited 44% (19/43), inhibited 37% (16/43) and had no effect on 19% of periaqueductal gray cells. The onset of D,L-homocystic acid-evoked responses ranged from 2 to 60 s; the duration of responses ranged from 1 to 18 min. Low-frequency, single-pulse electrical stimulation of proisocortex robustly altered neuronal discharge in 25% of periaqueductal gray neurons sampled; 10% (74/724) of neurons were excited and 15% (107/724) were inhibited. Insular cortex-evoked excitatory responses had a mean onset latency of 19.5 +/- 4.2 ms and a mean duration of 38.5 +/- 26.9 ms. Inhibitory responses had a mean onset latency of 26.2 +/- 15.6 ms and mean duration of 108.0 +/- 84.9 ms. Trains of high-frequency electrical stimulation of proisocortex excited 22% (13/59) and inhibited 25% (15/59) of periaqueductal gray cells tested. In separate experiments, stimulation electrodes were placed in periaqueductal gray to antidromically activate proisocortex neurons that project to periaqueductal gray.(ABSTRACT TRUNCATED AT 250 WORDS)
Amino Acids↗
Identification of tRNAs incorporated into wild-type and mutant human immunodeficiency virus type 1.
We have identified the tRNAs which are incorporated into both wild-type human immunodeficiency virus type 1 strain IIIB (HIV-1IIIB) produced in COS-7 cells transfected with HIV-1 proviral DNA and mutant, noninfectious HIV-1Lai particles produced in a genetically engineered Vero cell line. The mutant proviral DNA contains nucleotides 678 to 8944; i.e., both long terminal repeats and the primer binding site are absent. As analyzed by two-dimensional polyacrylamide gel electrophoresis, both mutant and wild-type HIV-1 contain four major-abundance tRNA species, which include tRNA(1,2Lys), tRNA(3Lys) (the putative primer for HIV-1 reverse transcriptase) and tRNA(Ile). Identification was accomplished by comparing the electrophoretic mobilities and RNase T1 digests with those of tRNA(3Lys) and tRNA(1,2Lys) purified from human placenta and comparing the partial nucleotide sequence at the 3' end of each viral tRNA species with published tRNA sequences. Thus, the absence of the primer binding site in the mutant virus does not affect tRNA(Lys) incorporation into HIV-1. However, only the wild-type virus contains tRNA(3Lys) tightly associated with the viral RNA genome. The identification of the tightly associated tRNA as tRNA(3Lys) is based upon an electrophoretic mobility identical to that of tRNA(3Lys) and the ability of this RNA to hybridize with a tRNA(3Lys)-specific DNA probe. In addition to the four wild-type tRNA species, the mutant HIV-1-like particle contains two tRNA(His) species and three tRNA-sized species that we have been unable to identify. Their absence in wild-type virus makes it unlikely that they are required for viral infectivity.
Acquired Immunodeficiency Syndrome↗
[Experimental studies on therapeutic effect of rat monoclonal antibody-bleomycin A6 conjugate against human colorectal cancer].
Bleomycin A6 (A6), a single component of bleomycin complex, is highly active against human colon and cecum cancer cells in vitro and xenografts in nude mice. R19, a rat monoclonal antibody against human cecum cancer Hce-8693 cells, was linked to A6. R19-A6 conjugate retained complete activity of McAb R19 and 10% activity of A6. As determined by clonogenic assay with human cecum cancer Hce-8693 cells for 1 hour exposure. The 50% inhibitory concentration (IC50) values for R19-A6, A6 and M3-A6 (conjugate of irrelevant Mc-A6) were 0.019, 1.05 and 1.00 mumol/L, respectively. The effect of the conjugate R19-A6 was 55-fold stronger than that of free A6 and 53-fold than irrelevant conjugate M3-A6. Clonogenic assay with human colon cancer HT-29 cells showed that the IC50 values were 0.078 mumol/L and 4.0 mumol/L for R19-A6 and free A6, respectively. The cytotoxicity to Hce-8693 and HT-29 cells was markedly blocked by unconjugated McAb R19 but not by irrelevant McAb MARK-3. The R19-A6 conjugate exerted 90% inhibition on the growth of cecum cancer Hce-8693 xenografts in nude mice, whereas equivalent doses of free A6, R19 plus A6 mixture and M3-A6 showed 52%, 34% and 48% inhibition, respectively. Histopathological examination showed no toxic changes in the heart, lung, liver, kidney and bone marrow in the R19-A6 conjugate treated animals.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
[Small molecule ribonuclear components and ribonucleoprotein complex antigens and rheumatic diseases].
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Antigens↗
[The control of somatosensory area II on the descending inhibiting pain activity of nucleus raphe magnus].
The aim of the present work is to observe the effects of somatosensory area II (Sm II) on the descending inhibiting pain activity of nucleus raphe magnus (NRM). The unit discharges in NRM and its responses to noxious stimulation of tail tip were extracellularly recorded with glass microelectrode. The bilateral Sm II was stimulated by fixed electrodes. Electroacupuncture (EA) of "Zusanli" was applied for 5 minutes. Both effects were compared at the same NRM neurons. It was found that stimulation of Sm II could activate the excitatoy-neurons in NRM (n = 10), significantly increasing their spontaneous discharges and decreasing their nociceptive responses during 0-20 minutes (P < 0.05-0.001). Similar results were observed after "Zusanli" EA, increase of their spontaneous discharges during 0-10 minutes and at 20th minute, and decrease of their nociceptive responses during 0-25 minutes were statistically significant (P < 0.05-0.001). The results were analysed with the linear regression, it was shown that the effects of Sm II stimulation and "Zusanli" EA on the spontaneous discharges and their nociceptive responses of NRM neurons were very similar in level and trend, being the positive correlation (P < 0.01-0.001). It is suggested that Sm II can activate the excitatory neurons in NRM, and it is possible that the effect of EA of "Zusanli" on NRM neurons is partially caused by activating Sm II.
Acupuncture Analgesia↗
[Antitumor effect of the immunoconjugate composed of antibiotic C1027 and Fab fragment from a monoclonal antibody directed against human hepatoma].
Antibiotic C1027, a macromolecular peptide with highly potent cytotoxicity to cultured cancer cells, was conjugated to monoclonal antibody 3A5 and its Fab fragment separately using SPDP as the linker agent. McAb 3A5, identified as IgG1, was directed against human hepatoma BEL-7402 cells. By ELISA, McAb 3A5 and the Fab fragment were strongly reactive with hepatoma cells and weakly reactive with KB cells. Determined by clonogenic assay against hepatoma BEL-7402 cells, the IC50 values for McAb-C1027, Fab-C1027 and C1027 were 4.2 x 10(-14), 8.6 x 10(-16) and 6.5 x 10(-16) mol.L-1, respectively. Fab-C1027 was 49-fold more potent than McAb-C1027 in cytotoxicity. Moreover, Fab-C1027 was 160-fold more potent in cytotoxicity to hepatoma cells than to KB cells, indicating selective cytotoxicity of Fab-C1027 conjugate to the target cells. Therapeutic effect of the conjugate was evaluated with hepatoma BEL-7402 xenograft in nude mice. After subcutaneous transplantation of the tumor, treatment started on day 3, iv, with equivalent dose of C1027, 0.1 mg.kg-1 x 6. Fab-C1027 and free C1027 inhibited tumor growth by 85% and 59%, respectively. Fab-C1027 conjugate showed more marked antitumor effect in vivo than free C1027.
Aminoglycosides↗
[The preparation and identification of anti-erythropoietin monoclonal antibodies].
By using the partially purified recombinant human erythropoietin (rHuEPO) as an antigen, two hybridoma clones have been obtained that secrete monoclonal antibodies against human erythropoietin. Intrasplenic immunization was successfully used in this experiment. The prepared monoclonal antibodies showed high specificity to human EPO by Ouchterlony, ELISA, dot blot and Western blot tests. They were also found to inhibit the biological activity of rHuEPO in a concentration-dependent manner by an in vitro bioassay. In the future, these monoclonal antibodies will be used as the solid phase antibodies in an enzyme-linked immunosorbent assay and as a probe for the purification of native erythropoietin and for the further studies of the hormone and its mechanism of action.
Animals↗
CT detection of wrist bone erosion in rheumatoid arthritis.
A correlative radiographic and CT study of the wrists of 30 patients with rheumatoid arthritis (RA) was reported. The results showed that sensitivity of CT in detecting wrist erosion is superior to that of conventional radiograph. Accordingly, wrist CT scanning is useful for early diagnosis of RA.
Adult↗
An opsin homologue in the retina and pigment epithelium.
PURPOSE: The aim of this project was to investigate the retinal pigment epithelium (RPE) at the molecular level by identification of novel RPE-specific cDNAs that may encode proteins of signal transduction pathways or other proteins that are expressed preferentially in the RPE. METHODS: A bovine RPE cDNA library was constructed in bacteriophage lambda g10 using RPE-enriched poly(A)+ RNA. The library was screened by differential hybridization to bovine RPE and kidney cDNA probes. RESULTS: A member of the hepatahelical receptor family was identified in bovine RPE by molecular cloning. Its deduced amino acid sequence predicts a protein that has 291 amino acid residues and resembles most closely the family of visual pigments. A lysine residue, analogous to the retinaldehyde attachment site in rhodopsin, is conserved in the seventh hydrophobic segment of the novel sequence. Messenger RNA encoding the putative G protein-coupled receptor was detected by in situ hybridization in the RPE, inner nuclear layer, and specific cells of the ganglion cell layer. Immunohistochemical staining of bovine retina showed that the receptor protein is localized in Müller cells, as well as in the RPE. CONCLUSIONS: A novel heptahelical receptor defines a distant evolutionary branch of the visual pigment tree. The selective localization of this putative receptor, its abundance in RPE and retina, and its homology to the visual pigments suggest that the function of this receptor is important in a visual process involving the RPE and Müller cells.
Amino Acid Sequence↗
Cyclic adenosine 3'5'-monophosphate potentiates excitatory amino acid and synaptic responses of rat spinal dorsal horn neurons.
Intracellular recordings were made from rat dorsal horn neurons in the in vitro slice preparation to study the actions of cyclic adenosine 3',5'-monophosphate (cyclic AMP). In the presence of TTX, bath application of the membrane permeable analogue of cyclic AMP, 8-Br cyclic AMP (25-100 microM) caused a small depolarization of the resting membrane potential accompanied by a variable change in membrane input resistance. In addition, 8-Br cyclic AMP caused a long-lasting increase in the spontaneous synaptic activity and the amplitude of presumed monosynaptic excitatory postsynaptic potentials evoked in the substantia gelatinosa neurons by orthodromic stimulation of a lumbar dorsal root. When the fast voltage-sensitive Na conductance was blocked by TTX, 8-Br cyclic AMP enhanced in a reversible manner, the depolarizing responses of a proportion of dorsal horn neurons to N-methyl-D-aspartic acid (NMDA), alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), quisqualic acid (QA) and kainic acid (KA). The effects of 8-Br cyclic AMP on the resting membrane potential and the NMDA response of dorsal horn neurons were mimicked by reducing phosphodiesterase activity with bath application of 3-isobutyl-1-methylxanthine, but not by cyclic AMP applied extracellularly. Moreover, we have found that intracellular application of a protein inhibitor of cyclic AMP-dependent protein kinase (PKI) into dorsal horn neurons prevents the 8-Br cyclic AMP-induced potentiation of the NMDA response of these cells. These results suggest that in the rat spinal dorsal horn the activation of the adenylate cyclase-cyclic AMP-dependent protein kinase system may be involved in the enhancement of the sensitivity of postsynaptic excitatory amino acid (NMDA, AMPA, KA) receptors and modulation of primary afferent neurotransmission, including nociception.
8-Bromo Cyclic Adenosine Monophosphate↗
Spin-flip-induced hole burning in GaAs quantum wells: Determination of the exciton Zeeman splitting.
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Journal Article↗
Variable tRNA content in HIV-1IIIB.
Low molecular weight RNA in HIV-1 is found in three size classes resembling 7S RNA, 5S RNA, and tRNA. The 2-dimensional polyacrylamide gel electrophoresis (2D PAGE) patterns of tRNA found in HIV-1 have been determined in virus produced in five different cell types: H9, UHC1 (a U937-derived clone), UHC8 (an RT(-) derivative of U937), HeLa, and COS. The presence of the putative primer tRNA for reverse transcriptase, tRNA(Lys,3), has also been determined either by hybridization with a tRNA(Lys,3)-specific DNA probe or by a comparison of the electrophoretic mobility of viral tRNA species with purified human tRNA(Lys,3). Our results indicate the following: 1) The number of tRNA species found in infectious HIV-1IIIB produced in different cell types varies, according to cell type, from greater than 20 to 4, indicating that only 4 or less tRNA species are required for the viral infectious life cycle. 2) There are 1-3 tRNA species tightly associated to the viral genomic RNA, depending upon the cell type producing the virus. 3) The putative primer tRNA, tRNA(Lys,3), is detected with the tRNA(Lys,3)-specific hybridization probe in the tRNA of HIV-1 produced in H9 cells, and the tightly associated tRNA species in this virus has the same electrophoretic mobility in 1-D PAGE as purified tRNA(Lys,3). On the other hand, we cannot detect tRNA(Lys,3) in the tRNA of HIV-1 produced in HeLa cells, and the tightly associated tRNA found in this virus does not migrate with the same electrophoretic mobility as tRNA(Lys,3).
Animals↗
Isolation and fractionation of retroviral tRNAs.
Previous studies concerning the analysis of retroviral tRNA populations involved intracellular metabolic labeling of RNA, followed by the isolation of viral RNA and lengthy sucrose gradient centrifugation for the separation of tRNAs found in various viral compartments. A more rapid, convenient, and safer method for achieving similar aims is described. Isolated total viral RNA is end-labeled in vitro, and tRNA subgroups are fractionated using commercial Nucleobond AX-20 mini columns. 2-D PAGE analysis of mouse mammary tumor virus tRNA fractionated in this way yields gel patterns similar to those obtained with previously described methods.
Chromatography↗
High-level expression of staphylococcal nuclease R gene in Escherichia coli.
Staphylococcal nuclease R, an analogue of nuclease A, was overproduced under the transcriptional control of the bacteriophage lambda PRPL promoters regulated by temperature sensitive repressors. The expression level reached 200-300 mg l-1 and showed little host dependence in different strains. The investigations of the recombinant nuclease R have revealed that the amino terminal formyl methionine residue of the nuclease is precisely processed, the protein consists of 155 amino acid residues. The experiment shows that the pBV221-DH5 alpha is a quite suitable vector-host system for high-level expression and precise processing of heterologous genes in Escherichia coli. The comparative studies between the codons used in the staphylococcal nuclease R gene and the optimal codon usage in E. coli indicate that high level expression of heterologous genes in E. coli may not always require a high degree of codon usage bias.
Amino Acid Sequence↗
Actions of epinephrine on neurons in the rat midbrain periaqueductal gray maintained in vitro.
The effect of epinephrine (EPI) on the activity of 150 periaqueductal gray (PAG) neurons was examined using extracellular recordings in an in vitro slice preparation. Drop application of EPI inhibited 45%, excited 35%, and had no effect on 20% of PAG neurons. Both the excitatory and inhibitory effects of EPI were of long duration; excitatory responses averaged 17 min and inhibitory responses averaged 11 min in duration. EPI responses could be blocked by specific alpha-1 and alpha-2 receptor antagonists. In 35% of the neurons tested, blockade of synaptic transmission by perfusion with low calcium-high magnesium physiological saline blocked responses to EPI. The effects of EPI were site specific: 77% of the cells in the caudal ventrolateral region of the PAG were inhibited by EPI; in all other regions of PAG equal numbers of cells were excited and inhibited by EPI. It is concluded that: (a) EPI has potent effects on a majority (80%) of PAG neurons; (b) EPI responses are mediated by presynaptic as well as postsynaptic mechanisms; (c) EPI preferentially inhibits neurons in the ventrolateral subdivision of caudal PAG. As this part of PAG contains many neurons that project to the ventral medulla, it is possible that EPI modulates the PAG-medullary functions such as analgesia, autonomic regulation, defense reactions, and sexual behaviors.
Animals↗