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A C Yu

Publications and source records attributed to A C Yu.

At least 19 recordsLinked to original sources
PubMed1995

Astrogliosis in culture. IV. Effects of basic fibroblast growth factor.

Previous studies have shown that the mechanical wounding of 3-week-old cultured rat astrocytes results in cell proliferation and hypertrophy resembling astrocyte responses to a brain injury in vivo. We now report the effects of basic fibroblast growth factor (bFGF) and an anti-bFGF antibody on astrocyte morphology, proliferation, and migration following in vitro wounding of confluent secondary cultures. Addition of bFGF (20 ng/ml) to wounded cultures induced morphological changes characteristic of differentiation in wounded and nonwounded areas of the culture. Combined treatment with bFGF and an anti-bFGF antibody (100 micrograms/ml) prevented this effect. Astrocyte proliferation along the edges of a scratch wound was at maximum 24 hr after wounding in cells growing in Eagle's minimum essential medium (EMEM) containing 10% serum. Low serum concentration and treatment with dibutyryl cyclic adenosine monophosphate (dbc-AMP) reduced injury-associated astrocyte proliferation. Addition of bFGF to cultures in EMEM with serum increased astrocyte proliferation at 18 and 24 hr after wounding. This effect was reduced considerably by treatment of cultures with bFGF in combination with an anti-bFGF antibody. The combined treatment and the antibody alone reduced cell division to a level lower than in control cultures. Twenty-four hr following wounding, astrocytes along the edges of the wound exhibited extension of thick, flat processes into the wound area. At 3 and 5 days after wounding, a bodily migration of astrocytes into the wounded area was observed. Addition of bFGF significantly increased astrocyte migration 1 day after wounding, with maximum effect on day 3 and no subsequent increase on day 5. A combination of bFGF and anti-bFGF antibody as well as the antibody alone reduced astrocyte migration to a level lower than in controls. Immunohistochemical localization and isoform pattern of bFGF in astrocytes did not change with dbc-AMP treatment or wounding. We conclude that mechanically wounded confluent astrocytes respond to bFGF added to the culture medium by enhancing cell division, differentiation, and migration. In addition, the results of the antibody treatment also suggest a role for endogenous bFGF in astrocyte proliferation and migration elicited by wounding in vitro. These results support the notion that in vivo, both bFGF released by injury and endogenous bFGF synthesized by astrocytes, contribute to the cellular responses that lead to astrogliosis.

Animals↗
PubMed1995

Gene expression in astrocytes during and after ischemia.

Involvement of the IEGs in brain injury and ischemia is under intensive investigation (Gubits et al., 1993). There are several families of the IEGs. They include the fos, jun, and zinc finger genes that encode transcription factors. Products of the fos family (c-fos, fra-1, fra-2, and fos B) bind to members of the jun family (c-jun, jun B, jun D) via leucine zippers, and this dimer then binds to the AP-1 site (consensus sequence -TGACTCA-) in the promoter of target genes, which in turn regulate the expression of late response genes that produce long-term changes in cells. For example, c-fos may regulate the long-term expression of preproenkephalin, nerve growth factor, dynorphin, vasoactive intestinal polypeptide, tyrosine hydroxylase and other genes with AP-1 sites in their promoters (Curran and Morgan, 1987; Sheng and Greenberg, 1990). It is likely that the c-fos gene up-regulation observed in ischemic astrocytes leads to the changes observed in the expressions of hsp and cytoskeleton protein genes in this experimental model. This is supported by the findings of Sarid (1991) and Pennypacker et al. (1994) who have shown that AP-1 DNA binding activity in hippocampus recognized an AP-1 sequence from the promoter region of the GFAP which is a potential target gene. van de Klundert et al. (1992) also suggested the involvement of AP-1 in transcriptional regulation of vimentin. IEGs can be induced within minutes by extracellular stimuli including transmitters, peptides, and growth factors. In this study, we have shown that c-fos induction by ischemia was rapid and transient.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Tumor necrosis factor-alpha and basic fibroblast growth factor decrease glial fibrillary acidic protein and its encoding mRNA in astrocyte cultures and glioblastoma cells.

Tumor necrosis factor-alpha is a pluripotent cytokine that is reportedly mitogenic to astrocytes. We examined expression of the astrocyte intermediate filament component glial fibrillary acidic protein in astrocyte cultures and the U373 glioblastoma cell line after treatment with tumor necrosis factor-alpha. Treatment with tumor necrosis factor-alpha for 72 h resulted in a decrease in content of glial fibrillary acidic protein and its encoding mRNA. At the same time, tumor necrosis factor-alpha treatment increased the expression of the cytokine interleukin-6 by astrocytes. The decrease in glial fibrillary acidic protein expression was greater when cells were subconfluent than when they were confluent. Thymidine uptake studies demonstrated that U373 cells proliferated in response to tumor necrosis factor-alpha, but primary neonatal astrocytes did not. However, in both U373 cells and primary astrocytes tumor necrosis factor-alpha induced an increase in total cellular protein content. Treatment of astrocytes and U373 cells for 72 h with the mitogenic cytokine basic fibroblast growth factor also induced a decrease in glial fibrillary acidic protein content and an increase in total protein level, demonstrating that this effect is not specific for tumor necrosis factor-alpha. The decrease in content of glial fibrillary acidic protein detected after tumor necrosis factor-alpha treatment is most likely due to dilution by other proteins that are synthesized rapidly in response to cytokine stimulation.

Animals↗
PubMed1995

Adult height in women with early-treated congenital adrenal hyperplasia (21-hydroxylase type): relation to body mass index in earlier childhood.

To investigate if obesity, as judged by increased body mass index (BMI), during childhood is associated with impaired adult stature in patients with 21-hydroxylase-type congenital adrenal hyperplasia (CAH), a retrospective analysis was carried out on outpatient records of 30 girls with CAH who had reached adult height. Height SD score for age (HtSDS(ca)), HtSDS for bone age (HtSDS(ba)), BMI and steroid dosage in early childhood (3.2-4.6 years) and later childhood (7.2-9.1 years), were compared with adult HtSDS (HtSDS(adlt)), adult HtSDS less mid-parental HtSDS (HtSDS(adlt)-HtSDS(mp)), predicted adult height SDS (HtSDS(pdct)), adult height SDS less predicted adult HtSDS (HtSDS(adlt)-HtSDS(pdct)) and age at menarche. Mean (SD) for HtSDS(adlt) was -1.13 (1.05), mean HtSDS(pdct) -0.12 (0.9) and mean age at menarche 13.5 (1.9) years. BMI in childhood was not correlated with HtSDS(adlt) but showed negative correlations with HtSDS(adlt)-HtSDS(mp) (r = -0.43; p < 0.02) and HtSDS(adlt)-HtSDS(pdct) (r-0.45; p < 0.02). BMI in later childhood showed negative correlations with HtSDS(adlt)-HtSDS(pdct) (r = -0.61; p < 0.001) and age at menarche (r = -0.63; p < 0.001). We conclude that in girls with early-treated CAH, a high BMI during early childhood is associated with loss of genetic height potential, and in later childhood with over-prediction of adult height and early menarche.

Adolescent↗
PubMed1994

Astrogliosis in culture: III. Effect of recombinant retrovirus expressing antisense glial fibrillary acidic protein RNA.

Injury to the central nervous system (CNS) either from trauma or due to demyelinating/degenerating diseases results in a typical response of astrocytes, termed astrogliosis. This reaction is characterized by astrocyte proliferation, extensive hypertrophy of nuclei, cell body, and cytoplasmic processes and an increase in immunodetectable glial fibrillary acidic protein (GFAP). GFAP accumulation may cause a physical barrier preventing the reestablishment of a functional environment. Our studies have aimed at modulating astrogliosis by inhibiting or delaying GFAP synthesis in damaged and reactive astrocytes. The present study investigates the use of a recombinant retrovirus expressing antisense GFAP RNA in controlling the response of mechanically injured astrocytes. A 650 bp fragment from the coding region of mouse GFAP cDNA was cloned in the antisense orientation under the control of long terminal repeat (LTR) promoter of Moloney murine leukemia virus. Increase in GFAP as detected by immunocytochemical staining in injured astrocytes was inhibited by treatment with retrovirus expressing antisense GFAP RNA. Also, astrocytes at the site of injury in these scratched cultures did not show cell body hypertrophy compared to control cultures. These observations demonstrate that the increase in GFAP at the site of injury can be inhibited using retroviral treatment and indicate the potential of retrovirus-mediated gene transfer in modulating scar formation in the CNS in vivo. These studies also shed light on the role of GFAP in maintaining the morphology of astrocytes.

Animals↗
PubMed1994

Distributed representation in the song system of oscines: evolutionary implications and functional consequences.

This paper reviews the organizational principles and implications that have emerged from the analysis of HVc, a forebrain nucleus that is a major site of sensory, motor, and sensorimotor integration in the song control system of oscine passerine birds (songbirds). Anatomical, physiological, and behavioral data support the conclusion that HVc exists within a hierarchically organized system with parallel pathways that converge onto HVc. The organization of HVc is distributed and redundant, and its outputs exhibit broad divergence. A similar pattern of connectivity exists for neostriatum adjacent to HVc. This and other data support the hypothesis that the song system arose from an elaboration or duplication of pathways generally present in all birds. Spontaneous and auditory response activity is strongly correlated throughout HVc, with auditory responses exhibiting strong temporal modulation in a synchronized fashion throughout the nucleus. This suggests that the auditory representation of song is encoded in the synchronized temporal patterns of activation, and that the predominant selectivity for the individual's own song that is observed for HVc neurons results from interactions of auditory input with central pattern generators for song. Most, or all HVc neurons are recruited during singing. The auditory response and motor recruitment properties of individual HVc neurons have no simple relationship, and the spontaneous activity in HVc may build up in the seconds preceding a song. To the extent HVc participates in perceptual phenomena associated with song, production and perception are not tightly linked in adults but may be linked by shared developmental processes during periods of sensorimotor learning.

Animals↗
PubMed1993

Reverse transcription and polymerase chain reaction technique for quantification of mRNA in primary astrocyte cultures.

The reverse transcription and polymerase chain reaction technique (RT-PCR) was assessed for the quantification of changes in mRNA levels from primary astrocyte cultures. The effects of dibutyryl cyclic AMP (dBcAMP) on glial fibrillary acidic protein (GFAP) mRNA and the effects of tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), and lipopolysaccharide (LPS) on interleukin-6 (IL-6) mRNA were examined. Two quantitative PCR methods were used: one involved carrying out the reaction in the exponential phase and the other involved the coamplification of a competitive target sequence. Increased GFAP mRNA in response to chronic dBcAMP treatment and increased IL-6 mRNA in response to TNF-alpha/IL-1 beta were readily detected. Both RT-PCR techniques were found to be suitable for the detection of large as well as smaller (twofold) changes in mRNA levels. The advantages and limitations of RT-PCR for mRNA quantification are discussed.

Animals↗
PubMed1992

Uptake and metabolism of malate in neurons and astrocytes in primary cultures.

Uptake and oxidative metabolism of [14C]malate as well as its incorporation into aspartate, glutamate, glutamine, and GABA were studied in cultured cerebral cortical neurons (GABAergic), cerebellar granule neurons (glutamatergic), and cerebral cortical astrocytes. All cell types exhibited high affinity uptake of malate (Km 10-85 microM) with slightly higher Vmax values in neurons (0.1-0.2 nmol x min-1 x mg-1) than in astrocytes (0.06 nmol x min-1 x mg-1). Malate was oxidatively metabolized in all three cell types with nominal rates of 14CO2 production of 2-15 pmol x min-1 x mg-1. The oxidation of malate was only slightly inhibited by 5 mM aminooxyacetic acid (AOAA). In granule cell preparations [14C]malate was incorporated into aspartate and glutamate and, to a much less extent, into glutamine. This incorporation was blocked by 5 mM AOAA. Astrocytes exhibited slightly higher incorporation rates into aspartate and glutamate, but in these cells glutamine was labelled to a considerable extent. AOAA (5 mM) inhibited the incorporation by 60-70%. In cultures of cerebral cortical neurons, very low levels of radioactivity derived from [14C]malate were found in aspartate and glutamate, and GABA was not labelled at all. Glutamine had the same specific activity as glutamate, indicating that the low rates of incorporation of radioactivity into amino acids in this preparation is likely to exclusively represent metabolism of malate in the small population of astrocytes (5% of total cell number), contaminating the neuronal cultures. The findings suggest that exogenous malate to a quantitatively limited extent may serve as a precursor for transmitter glutamate in glutamatergic neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Selective brain cooling during and after prolonged global ischemia reduces cortical damage in rats.

BACKGROUND AND PURPOSE: Studies of the cerebroprotective effects of selective brain cooling have failed to show amelioration of ischemic injury in the cerebral cortex. This study was designed to test the hypothesis that mild-to-moderate selective brain cooling initiated after the onset of global brain ischemia in rats protects the cerebral cortex and improves neurological outcome. METHODS: Global forebrain ischemia for 30 minutes in 27 fasted adult male Wistar rats was achieved by bilateral carotid occlusion and hypotension. In group 1, brain temperature, measured in the temporalis muscle, was maintained at 37-38 degrees C throughout the experiment. In group 2, brain temperature fell spontaneously during ischemia to 34.7 +/- 0.1 degrees C and rose spontaneously to 36-37 degrees C after 10 minutes of recirculation. In group 3, brain temperature was lowered with ice packs placed around the head after 15 minutes of ischemia to 24.1 +/- 0.9 degrees C by the end of ischemia, maintained at 30.0 +/- 1.0 degrees C for the first hour of recirculation, then allowed to rise to 36-37 degrees C. RESULTS: Seven-day survival was 0% (0 of 6) in group 1, 73% (8 of 11) in group 2, and 100% (6 of 6) in group 3. Severity of neuronal damage was less in group 2 than in group 1 in the cortex (p < 0.05) and hippocampal CA1 (p < 0.05) and CA3 regions (p < 0.05). Group 3 had less neuronal damage than group 2 in both cortex (p < 0.02) and striatum (p < 0.02). Furthermore, postischemic weight loss was less and neurobehavioral scores were significantly higher in group 3. CONCLUSIONS: This study shows that selective brain cooling increases survival from prolonged global ischemia and reduces neuronal injury in the cerebral cortex as well as the striatum and hippocampus.

Animals↗
PubMed1991

Inhibition of GFAP synthesis by antisense RNA in astrocytes.

Glial fibrillary acidic protein (GFAP) accumulation is a prominent feature of astrocytic gliosis. The inhibition or delay in GFAP synthesis might delay scar formation resulting from an insult such as spinal cord injury or central nervous system (CNS) demyelination. The delay in the formation of a physical barrier might allow the neurons and oligodendrocytes to reestablish a functional environment. We delivered antisense GFAP RNA complexed with Lipofectin (LF), a cationic liposome, into cerebral astrocytes in culture and tested the feasibility of inhibiting GFAP synthesis. Our results demonstrate that LF facilitated antisense RNA uptake into astrocytes. Astrocytes took up 3H-antisense GFAP RNA alone and reached an equilibrium of 7-8.8 eta g per mg protein after 2.5 hr. When complexed with LF, astrocytes could increase the uptake to 14 eta g per mg protein and the time for reaching this quantity was shortened to 10 min. This uptake level was further enhanced if experiments were carried out in HEPES buffered saline (HBS). All uptake studies were dose- and time-dependent. Dibutyryl cyclic AMP (dBcAMP) is known to induce an increase of GFAP content in cultured astrocytes. We studied the effect of LF/antisense GFAP RNA on the GFAP content in dBcAMP (0.25 mM)-treated astrocytes. Cultures of astrocytes treated with dBcAMP contained almost twice as much GFAP as untreated cultures after 2 days. Similar cultures treated with LF/antisense RNA in HBS did not show an increase but a 30-40% decrease in GFAP content 2 days after treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Fructose-1,6-bisphosphate reduces ATP loss from hypoxic astrocytes.

Hypoxia caused injury and metabolic dysfunction of astrocytes, as indicated by a time-dependent loss of lactate dehydrogenase (LDH) activity and ATP content. The combination of 3.5 mM fructose-1,6-bisphosphate (FBP) and 7.5 mM glucose (GLC) reduced the decrease of ATP and prevented the loss of LDH. These data indicate that the combination of GLC + FBP protects astrocytes from hypoxia. The results also suggest that the maintainance of ATP concentration is the mechanism by which FBP prevents hypoxic injury.

Adenosine Triphosphate↗
PubMed1990

Phagocytosis of peripheral nerve myelin in vitro: effect of antibody.

We have previously shown that antisera to whole CNS myelin, whole PNS myelin, galactocerebroside (GC), and myelin basic protein (MBP) promote the uptake of CNS myelin by cultured macrophages, and stimulate the conversion of myelin lipids to cholesterol ester and triglycerides. Here we report the results of similar studies using PNS myelin purified from the rat sciatic nerve. Antisera to whole CNS myelin, whole PNS myelin, GC, and MBP preincubated with 14C-labeled PNS myelin increased the production of radioactive cholesterol ester by macrophages in culture to a level about twice that with preimmune serum, and five to six times that of untreated myelin. The amounts of [14C]triglyceride were similarly increased with these antisera, whole P0 and P2 antisera had little or no effect. IgG prepared from the antisera stimulated lipid metabolism to almost the same extent, while heating the antisera did not decrease the stimulatory effect, indicating that myelin was opsonized by IgG, but not likely by complement. With a few exceptions, the four active sera and their IgGs promoted the macrophage metabolism of CNS and PNS myelin almost equally. The cultured macrophages converted about 3% of untreated CNS myelin and about 6% PNS myelin cholesterol to cholesterol ester. Under phase contrast microscopy it was noted that vesicles of CNS myelin appeared to bind individually to macrophages, whereas PNS myelin vesicles tended to self-associate to form large clumps which were found to macrophages. Binding studies showed PNS myelin to be bound more firmly to macrophages than CNS myelin.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗