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Q Gu

Publications and source records attributed to Q Gu.

At least 109 records · Page 6Linked to original sources
PubMed1994

Nerve growth factor-induced ocular dominance plasticity in adult cat visual cortex.

Activity-dependent modifiability of cortical ocular dominance occurs only during early postnatal life, within the so-called "critical period," but not thereafter in adult visual cortex. To examine the role of neurotrophins in the activity- and age-dependent stimulation-induced modifiability of visual cortex, we tested whether intracortical infusion of nerve growth factor could induce ocular dominance plasticity in adult visual cortex. Nerve growth factor was continuously infused, by means of osmotic minipumps, into striate cortex of adult cats for 2 weeks. At the time of minipump implantation, one eyelid of the experimental animals was sutured closed. After 3 weeks of monocular deprivation, the ocular dominance distribution of neurons in the striate cortex was assessed using single unit recording. We found that monocular deprivation imposed on adult animals in conjunction with nerve growth factor infusion causes an ocular dominance shift toward the deprived eye. Although the underlying mechanisms remain uncertain, the results indicate that nerve growth factor can enhance activity-dependent synaptic modification and remodeling in adult visual cortex.

Age Factors↗
PubMed1994

Identification and characterization of SPRK, a novel src-homology 3 domain-containing proline-rich kinase with serine/threonine kinase activity.

Protein kinase play important roles in the growth and differentiation of cells. We have isolated cDNA clones from the human megakaryocytic cell line CMK11-5 that encode a novel protein kinase, which we call SPRK (src-homology 3 (SH3) domain-containing proline-rich kinase). The gene sequence predicts an 847-amino acid protein kinase with a unique domain arrangement. An amino-terminal glycine-rich region is followed by an SH3 domain and a kinase domain that is similar to both tyrosine and serine/threonine kinases. Adjacent to the kinase domain are two closely spaced leucine/isoleucine zipper motifs and a stretch of basic amino acids that resembles karyophilic nuclear localization signals. The COOH-terminal half of SPRK is basic, and proline accounts for 24% of the COOH-terminal 216 amino acids. The sprk gene is widely expressed as a 4-kilobase transcript in adult and fetal human tissues. Transfection of 293 cells with a vector encoding an epitope-tagged SPRK results in the expression of a 95-kDa protein. The epitope-tagged SPRK becomes phosphorylated on serine and threonine residues in an in vitro kinase assay, whereas SPRK variants with point mutations in the predicted ATP-binding site fail to become phosphorylated. These data indicate that SPRK has serine/threonine kinase activity. The SH3 domain of SPRK is interrupted by a unique 5-amino acid insert whose location in the SH3 consensus sequence is the same as that of the inserts found in the SH3 domains of neuronal SRC and of the p85 subunit of phosphatidylinositol 3-kinase.

Adult↗
PubMed1994

Involvement of muscarinic acetylcholine receptors in regulation of kitten visual cortex plasticity.

Receptor autoradiographic methods specific for M3 and M1 muscarinic acetylcholine receptors were used to investigate the development and input-dependent laminar redistribution of these receptor populations during the critical period for kitten visual cortex plasticity. Analysis of the binding curves of [3H]4-diphenylacetyl-N-methyl-piperidine (4-DAMP) and [3H]pirenzepine (PZ) indicated that these two ligands bound heterogeneously to muscarinic acetylcholine receptors with different affinities. While [3H]4-DAMP showed a high affinity for M3 receptors and much lower affinities for M1 and M2 receptors, [3H]PZ displayed higher affinity for M1 receptors. By carefully choosing concentrations of labelled and unlabeled ligands, the patterns of laminar distribution for both receptor subtypes within visual cortex were obtained. Both receptors were most concentrated in cortical layer IV immediately after birth and during the most sensitive period of visual cortex plasticity. The binding density for both receptor subtypes thinned out progressively in this layer to concentrate in more superficial layers as plasticity waned with age. Moreover, interruption of visual or spontaneous input to visual cortex induced either by lesion or by tetrodotoxin infusion into lateral geniculate nucleus prevented the developmental redistribution of these receptors from layer IV to superficial layers, that is, the pattern of laminar distribution remained that of the age at which the lesion or tetrodotoxin infusion into the lateral geniculate nucleus was performed. The results indicate that the developmental expression of M3 and M1 muscarinic acetylcholine receptors in kitten visual cortex depends on cortical inputs.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

rse, a novel receptor-type tyrosine kinase with homology to Axl/Ufo, is expressed at high levels in the brain.

We have isolated cDNA clones that encode the human and murine forms of a novel receptor-type tyrosine kinase termed Rse. Sequence analysis indicates that human Rse contains 890 amino acids, with an extracellular region composed of two immunoglobulin-like domains followed by two fibronectin type III domains. Murine Rse contains 880 amino acids and shares 90% amino acid identity with its human counterpart. Rse is structurally similar to the receptor-type tyrosine kinase Axl/Ufo, and the two proteins have 35 and 63% sequence identity in their extracellular and intracellular domains, respectively. To study the synthesis and activation of this putative receptor-type tyrosine kinase, we constructed a version of Rse (termed gD-Rse, where gD represents glycoprotein D) that contains an NH2-terminal epitope tag. NIH3T3 cells were engineered to express gD-Rse, which could be detected at the cell surface by fluorescence-activated cell sorting. Moreover, gD-Rse was rapidly phosphorylated on tyrosine residues upon incubation of the cells with an antibody directed against the epitope tag, suggesting that rse encodes an active tyrosine kinase. In the human tissues we examined, the highest level of expression of rse mRNA was observed in the brain; rse mRNA was also detected in the premegakaryocytopoietic cell lines CMK11-5 and Dami. The gene for rse was localized to human chromosome 15.

3T3 Cells↗
PubMed1994

A study of tachykinin-immunoreactivity in the cat visual cortex.

The localization of tachykinin-immunoreactivity in the cat visual cortex (area 17) was investigated using immunohistochemical methods. Strong laminar specificity was observed, with immunoreactivity highest in layer V, followed by layers I, VI, II and III, and the lowest density in layer IV. Most of the immunoreactive product was localized in neuronal processes. A few immunopositive cell bodies were also present. The immunopositive neurons were non-pyramidal, multipolar, or bipolar in shape, and mostly found in layer V. There were particularly dense immunopositive fibers and varicosities around somata in layer V. These may represent tachykinin-containing presynaptic terminals (boutons). The results provide anatomical evidence that tachykinins may primarily affect layer V neurons in the cat visual cortex.

Animals↗
PubMed1994

Activity-dependent expression and distribution of M1 muscarinic ACh receptors in visual cortex neuronal cultures.

The fluorescently labeled muscarinic M1 receptor-selective antagonist BODIPY FL pirenzepine has been employed to study the activity-dependent distribution and expression of muscarinic M1 ACh receptors (M1AChRs) in cultured neurons derived from rat visual cortex. Displacement experiments showed that like pirenzepine, binding of BODIPY FL pirenzepine was specific to M1 receptors and its K(i) was similar to that of unlabeled pirenzepine. Using confocal laser scanning microscopy, M1 receptors were predominantly localized to cell bodies early in development in the culture environment. After 2 weeks in culture, the receptors showed labeling not only in cell bodies but also in neuritic processes, especially on the initial segments of the processes. Chronic membrane depolarization with 40 mM potassium chloride caused a dramatic increase in M1 receptor expression on these neurons. Conversely, blockade of neuronal activity with 0.1 microM TTX decreased expression of the receptors. Receptor expression increased after cells were treated chronically with 50 nM pirenzepine, whereas it decreased after exposure to 10 microM carbachol. The results demonstrate for the first time the exact location of muscarinic receptors in living cultured neurons and also the activity-dependent expression of M1 receptors on these neurons. Both chronic membrane depolarization and antagonist application upregulate receptor expression, whereas blocking bioelectrical activity or chronic agonist application downregulates expression.

Animals↗
PubMed1993

Immunocytochemical localization of enkephalin in the cat visual cortex.

The localization of enkephalin-immunoreactivity in the cat visual cortex (area 17) was analyzed by using immunohistochemical methods with a monoclonal antibody directed against enkephalin. The majority of the immunoreactive product was localized in neuronal processes. The density of immunopositive fibers was greatest in layer VI, with moderate staining in layers I, II, III and V, and the least dense staining in layer IV. Layer IVab neurons showed a striking concentration of immunopositive puncta around their cell bodies. Immunopositive neurons were scarcely present in the visual cortex. They were found in all cortical layers, but mostly in layer VI. The immunopositive neurons were non-pyramidal, mostly multipolar in shape and occasionally bipolar. The results provide anatomical evidence that enkephalin may have modulatory effects on visual cortical neurons.

Animals↗
PubMed1993

A tobacco gene family for flower cell wall proteins with a proline-rich domain and a cysteine-rich domain.

Flowering is known to be associated with the induction of many cell wall proteins. We report here five members of a tobacco gene family (CELP, Cys-rich extensin-like protein) whose mRNAs are found predominantly in flowers and encode extensin-like Pro-rich proteins. CELP mRNAs accumulate most abundantly in vascular and epidermal tissues of floral organs. In the pistil, CELP mRNAs also accumulate in a thin layer of cells between the transmitting tissue and the cortex of the style and in a surface layer of cells of the placenta in the ovary. This unique accumulation pattern of CELP mRNAs in the pistil suggests a possible role in pollination and fertilization processes. CELP genes encode a class of plant extracellular matrix proteins that have several distinct structural features: a Pro-rich extensin-like domain with Xaa-Pro3-7 motifs and Xaa-Pro doublets, a Cys-rich region, and a highly charged C terminus. The extensin-like domains in these proteins differ significantly in their length and these differences appear to be results of both long and short deletions within the coding regions of their genes. Furthermore, the number of charged amino acid residues in the C-terminal region varies among the CELPs. These structural differences may contribute to functional versatility in the CELPs. On the other hand, the Cys-rich domain is highly conserved among CELPs and the positions of the Cys residues are conserved, suggesting that this region may have a common functional role. The presence of a Pro-rich domain and a Cys-rich domain in these CELPs is reminiscent of a class of hydroxyproline-rich glycoproteins, solanaceous lectins, that are believed to be important in cell-cell recognition. The structure of these CELPs indicates that they may be multifunctional and that their genes may have arisen from recombinational events.

Amino Acid Sequence↗
PubMed1993

Immunocytochemical study of GABAA receptors in the cat visual cortex.

The laminar distribution and morphological structures associated with GABAA receptor immunoreactivity in the cat visual cortex were studied by using two different polyclonal antibodies directed either against the purified GABAA receptor protein (antibody "967") or against a specific domain of the beta 1-subunit of the GABAA receptor (antibody "Q"). Immunoblots of cat visual cortex tissue with these antibodies revealed that antibody "Q" recognizes only one subunit, namely the beta 1-subunit of the GABAA receptor, and that antibody "967" recognizes three subunits. Both antibodies produced very similar staining patterns, indicating that the beta 1-subunit may be an essential component of the GABAA receptor in the cat visual cortex. The typical staining pattern showed a clear membrane structure around neuronal somata. Using cell body shape criteria, immunopositive neurons included both pyramidal cells in cortical layers II, III, and V, and nonpyramidal cells in all cortical layers. Immunopositive neurons were uniformly distributed in layers II to VI, whereas the density of immunopositive cells in layer I was lower. Some immunopositive neurons were also found in the white matter underlying the visual cortex. In gray matter, immunopositive structures also included dendrites, especially the proximal dendrites, and axon initial segments of pyramidal neurons. The immunopositive processes usually ran vertically toward the pial surface. Some astrocytes were also immunostained. They were localized in layer I and in the white matter. The overall pattern of immunostaining was similar in areas 17, 18, and 19.

Amino Acid Sequence↗
PubMed1993

Effects of intracortical infusion of anticholinergic drugs on neuronal plasticity in kitten striate cortex.

During a critical period of postnatal development the mammalian visual cortex is highly susceptible to experience-dependent alterations of neuronal response properties. These modifications are facilitated by the neuromodulators noradrenaline and acetylcholine. To identify the cholinergic mechanisms responsible for this facilitation, muscarinic and nicotinic antagonists were infused into the visual cortex of kittens while the animals were subject to monocular deprivation. Subsequently the ocular dominance of cortical cells was assessed by single-unit recording. Ocular dominance changes were suppressed by scopolamine and pirenzepine but not by gallamine, hexamethonium and mecamylamine. This blocking effect was concentration-dependent, and control experiments revealed that it was not due to suppression of neuronal responses to light. It is concluded from these results that acetylcholine facilitates neuronal plasticity in the visual cortex through mechanisms activated by muscarinic M1 receptors.

Animals↗
PubMed1993

Immunocytochemical localization of calcineurin in the adult and developing primary visual cortex of cats.

An immunocytochemical method was used to localize calcineurin, a calcium-dependent calmodulin-stimulated protein phosphatase, in the primary visual cortex of developing and adult cats. In the adult calcineurin immunoreactivity exhibits a laminar distribution with dense labeling in the upper half of layers II/III and two lightly labeled bands in lower layer IV and in layer VI. Most of the immunoreactive neurons are pyramidal in shape and appear to form a subpopulation of cortical neurons, but non-pyramidal neurons were also labeled, especially during early stages of postnatal development. The distribution pattern of calcineurin immunoreactivity showed developmental changes until at least 3 months of age. The number of calcineurin-positive cells abruptly increased at 3 weeks, and heavily labeled neurons appeared in a well-delineated band in layer IV between 3 and 5 weeks of age. At 6 to 10 weeks, neurons in layers II/III also became strongly immunoreactive. At this developmental stage intensely stained cells were thus distributed throughout layers II to IV. Thereafter, there was a marked decrease in the number of immunoreactive cells in layer IV and beyond 12 weeks the distribution pattern of calcineurin immunoreactivity became similar to that of adult animals. These changes of calcineurin expression show some relation with the inside-out pattern of cortical maturation and with the time course and the laminar selectivity of use-dependent malleability. Therefore, we suggest that calcineurin may be involved in processes of neuronal differentiation and experience-dependent plasticity.

Aging↗
PubMed1993

An improved staining technique for cytochrome C oxidase.

Cytochrome C oxidase (CO) has been shown to be an indicator of neuronal activity in the brain. In the primate visual cortex, CO staining also differentiates cell populations encoding visual properties such as color, contrast, ocularity, and movement. We have developed a modified method which dramatically enhances the intensity and contrast of CO staining. This method can be applied to both fixed and non-fixed tissues. The sensitivity of this method is sufficiently high that, even after years of storage, tissues can still be well stained for CO activity. Such tissue is poorly stained with current methods. This CO staining technique may also be useful for double labeling of CO with other anatomical markers.

Animals↗
PubMed1993

Characterization of cDNAs for stylar transmitting tissue-specific proline-rich proteins in tobacco.

The pistil of flowers is a specialized organ which contains the female gametophytes and provides the structures necessary for pollination and fertilization. Pollen deposited on the stigmatic surface of a compatible plant germinates a pollen tube which penetrates the stigmatic papillae and grows intercellularly through the style towards the ovules in the ovary. Pollen tube growth is largely restricted to the transmitting tissue in the style. Therefore the stylar transmitting tissue is extremely important for the migration of the pollen cell towards the ovary. We have isolated two related cDNAs, transmitting tissue-specific (TTS)-1 and TTS-2, derived from two proline-rich protein (PRP)-encoding mRNAs that accumulate specifically in the transmitting tissue of tobacco. The deduced PRP sequences share similarities with proline-rich cell wall glycoproteins found in a variety of plants. TTS-1 and TTS-2 mRNAs are induced in very young floral buds, accumulate most abundantly during the later stages of flower development when style elongation is the most rapid, and remain at relatively high levels at anthesis. These mRNAs become undetectable in maturing green fruits. In situ hybridization shows that TTS-1 and TTS-2 mRNA accumulation is restricted to the transmitting tissue of the style. The possible roles that these transmitting tissue-specific PRPs may play in maintaining the structural integrity of the style or in the function of this organ is discussed.

Amino Acid Sequence↗
PubMed1992

Nonlinear response of biophoton emission to external perturbations.

By considering an exciplex system consisting of collective molecules in interaction with both the 'pumping' fields and the biophoton fields, the two-level exciplex model and the three-level exciplex model are presented. They are useful for the investigation of the quasi-stationary behaviour of biophoton emission, and biophoton emission as a dynamic process in the presence of external perturbations. Our theoretical results predict a series of nonlinear effects, such as chaos, fractal behaviour, and non-equilibrium phase transition. These effects characterize the coherence nature of living systems. In our approaches, there are two important quantities f and x, which can be used to mark the working points of the two-level and three-level exciplex systems. All the influences of external perturbations on the exciplex systems, e.g. change of temperature, the addition of agents, exposure to light, etc., can be interpreted as shifts of the working points of the systems, leading to a diversity of nonlinear response of biophoton emission. In addition, the agreements of the theoretical results and the corresponding experimental observations on biophoton emission from biological systems in the presence of external perturbations are demonstrated.

Mathematics↗
PubMed1992

Molecular cloning of the flavin-containing monooxygenase (form II) cDNA from adult human liver.

Complementary DNA (cDNA) clones encoding the adult human liver flavin-containing monooxygenase (FMO; dimethylaniline N-oxidase, EC 1.14.13.8) were isolated from lambda gt10 and lambda gt11 libraries. The cDNA libraries were screened with three synthetic 36-mer oligonucleotide probes derived from the nucleic acid sequence of the pig liver FMO cDNA. The deduced amino acid sequence for the adult human liver FMO was quite distinct from the pig liver FMO, and adult human liver FMO was designated form II (HLFMO II). The full-length cDNA sequence of HLFMO II [2119 base pairs (bp)] had an open reading frame of 1599 nucleotides, which encoded a 533-amino acid protein of Mr 59,179, a 5'-noncoding region of 136 nucleotides and a 3'-noncoding region of 369 nucleotides excluding the poly(A) tail. The deduced amino acid sequence of HLFMO II had 80% similarity with the rabbit liver FMO II but only a 52%, 55%, and 53% amino acid similarity with the rabbit liver (form I), the pig liver (form I), and fetal human liver (form I) FMOs, respectively. RNA analysis of adult human liver RNA showed that there was one HLFMO II mRNA species. Analysis of genomic DNA indicated that HLFMO II was the product of a single gene. These results indicated that the deduced amino acid sequence for HLFMO II contained highly conserved residues and suggested that FMO enzymes were closely related and, undoubtedly, derived from the same ancestral gene.

Amino Acid Sequence↗
PubMed1992

A flower-specific cDNA encoding a novel thionin in tobacco.

We isolated a flower-specific cDNA, FST (flower-specific thionin), which encodes a novel thionin from tobacco. Thionins are basic and cysteine (Cys)-rich, low molecular weight proteins found in many plants. They are believed to play a role in plant defense against pathogens. The central domain of the FST protein shares homology with three gamma-thionins. Like other thionin precursors, the FST protein has an N-terminal domain characteristic of a signal peptide and an acidic C-terminal domain. FST mRNA accumulates specifically in developing flowers and its level drops as flowers mature. Transcripts are present in petals, stamens and pistil but are not detectable in sepals. In situ hybridization revealed that FST mRNA is most abundant in the epidermal cells along the adaxial surface of petals, and in the surface cell layers of the carpel and anther walls. If the FST protein indeed has a protective role in flowers, this pattern of spatial distribution of FST mRNA would appear to maximize this effect on the two internal reproductive whorls. A possible biological role for FST is discussed.

Amino Acid Sequence↗
PubMed1992

GABAA receptor immunoreactivity in the white matter.

Using immunohistochemical methods with polyclonal antibodies directed against a specific sequence of the beta 1-subunit of the GABAA receptor, we found strong immunoreactivity in the white matter of cat brain. The immunopositive products were present primarily on processes of glial cells, especially astrocytes. Immunoreactivity appeared also on the cell bodies of astrocytes and on the cytoplasmic membranes of neurons. The abundant immunostaining in the white matter suggests that (1) GABAA receptors are present on glial cells in vivo, (2) GABAA receptors may be localized on non-synaptic membranes in the white matter and (3) activation of GABAA receptors may have some trophic effects on preservation of the structure and functional properties of the white matter.

Amino Acid Sequence↗