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Biomedical subjects

Y You

Publications and source records attributed to Y You.

At least 37 records · Page 2Linked to original sources
PubMed1999

[Genetic complementation group analysis of xeroderma pigmentosum patients in China].

OBJECTIVE: To establish skin fibroblast cell strains derived from Chinese xeroderma pigmentosum(XP) patients and to analyze the genetic complementation group and distribution. METHODS: From four XP patients, skin fibroblast cell strains were derived and used for the complementation group analysis by autoradiography and cell-fusion technique. RESULTS: Of the four XP patients from apparently independent families, three were assigned to group C, and one belonged to group E. This is the first report on XP-E patient in China. CONCLUSION: Based on the data from the previous 7 cases and the present 4 cases, the distribution of complementation group in Chinese XP patients known at present is: nine XP-C, one XP-F and one XP-E. Although the number of cases is still limited, XP-C appears to be more frequent in China. This forms a marked contrast to Japanese XP patients, who are dominated by XP-A with infrequent presence of XP-C.

Adolescent↗
PubMed1999

[The significance of pattern electroretinogram in detecting retinal function in primary open angle glaucoma].

OBJECTIVE: To evaluate the clinical significance of pattern electroretinogram (PERG) in primary open angle glaucoma (POAG). METHOD: Thirty-six patients (59 eyes) with POAG and 32 persons (59 eyes) as age-matched normal controls were tested by PERG. RESULTS: The changes of PERG in POAG included reduction of amplitudes of P(1), N(2), P(1) + N(2) and N(2)/P(1). Using the criteria of AN(2) + AP(1) < 2.7 and AN(2)/AP(1) < 0.7 (A = amplitude), the positive rate was 90% in 59 eyes with POAG, and no eye from the normal control group was considered as abnormal. The amplitudes of PERG had already been abnormal before the early visual field loss occurred in POAG eyes. The amplitudes of P(1) and N(2) waves decreased with the enlargement of visual field defect, were positively correlated to the patient's visual acuity and negatively correlated to the cup/disc ratio of optic nerve papilla, and linear regression equations between them were respectively established. CONCLUSION: PERG is an useful method in detecting the retinal functions in POAG.

Adult↗
PubMed1999

[Study on anticardiolipin antibody in the patients with primary nephrotic syndrome].

Combination of the anticardiolipin antibody with the phospholipids on the surfaces of the endothelia and thrombocytes can damage the basic functions of cells. In this study, the anticardiolipin antibody was detected in 68 cases with primary nephrotic syndrome and 30 healthy persons. The positive rates were 32.35% and 3.33%, respectively. The hypercoagulability and glomerular impairment in the positive cases were more evident than those in the negative cases. In addition, the sensitivity to treatment in the positive cases was markedly decreased. These findings indicate that the anticardiolipin antibody may play an important role in pathophysiological processes of primary nephrotic syndrome.

Adolescent↗
PubMed1998

Absence of cytokine receptor-dependent specificity in red blood cell differentiation in vivo.

Erythropoietin (EPO) is required for red blood cell development, but whether EPO-specific signals directly instruct erythroid differentiation is unknown. We used a dominant system in which constitutively active variants of the EPO receptor were introduced into erythroid progenitors in mice. Chimeric receptors were constructed by replacing the cytoplasmic tail of constitutively active variants of the EPO receptor with tails of diverse cytokine receptors. Receptors linked to granulocyte or platelet production supported complete erythroid development in vitro and in vivo, as did the growth hormone receptor, a nonhematopoietic receptor. Therefore, EPOR-specific signals are not required for terminal differentiation of erythrocytes. Furthermore, we found that cellular context can influence cytokine receptor signaling.

3T3 Cells↗
PubMed1998

Heteromerization of the gammac chain with the interleukin-9 receptor alpha subunit leads to STAT activation and prevention of apoptosis.

Interleukin-9 (IL-9) is a cytokine with pleiotropic effects on mast cell and T cell lines. It exerts its effects through the IL-9R complex consisting of IL-9Ralpha and the common gammac subunit. Here we report functional evidence for receptor heteromerization for efficient signal transduction, and we define minimal requirements in the two receptor subunits for IL-9R function. Tyrosine 336 of the IL-9Ralpha and the membrane-proximal segment of gammac are both crucial for signaling. The activated IL-9R complex employs the Janus kinases JAK1 and JAK3 for subsequent activation of the signal transducer and activator transcription (STAT) factors STAT-1, STAT-3, and STAT-5. This process is independent of Tyk2. We demonstrate further that the activated STAT complexes consist of STAT-1 and STAT-5 homodimers and STAT-1-STAT-3 heterodimers. Finally, we show that IL-9R signaling in a T cell line does not result in detectable mitogen-activated protein kinase activation and leads to unsustained proliferation. Nonetheless, these T cells are efficiently protected from dexamethasone-induced apoptosis. These results further define the molecular architecture of the IL-9R and its specific connections to various biologic responses.

Animals↗
PubMed1998

Redundant and selective roles for erythropoietin receptor tyrosines in erythropoiesis in vivo.

Cytokine receptors have been shown in cell culture systems to use phosphotyrosine residues as docking sites for certain signal transduction intermediates. Studies using various cellular backgrounds have yielded conflicting information about the importance of such residues. The present studies were undertaken to determine whether or not tyrosine residues within the erythropoietin receptor (EPOR) are essential for biologic activity during hematopoiesis in vivo. A variant of the EPOR was constructed that contains both a substitution (R129C) causing constitutive receptor activation as well as replacement of all eight cytoplasmic tyrosines by phenylalanines (cEPORYF). A comparison between animals exposed to recombinant retroviruses expressing cEPOR and cEPORYF showed that efficient red blood cell (RBC) development in vivo is dependent on the pressence of tyrosine residues in the cytoplasmic domain of the EPOR. In addition, an inefficient EPOR tyrosine independent pathway supporting RBC development was detected. Tyrosine add-back mutants showed that multiple individual tyrosines have the capacity to restore full erythropoietic potential to the EPOR as determined in whole animals. The analysis of primary erythroid progenitors transduced with the various cEPOR tyrosine mutants and tyrosine add-backs showed that only tyrosine 343 (Y1) and tyrosine 479 (Y8) were capable of supporting immature burst-forming unit-erythroid progenitor development. Thus, this receptor is characterized by striking functional redundancy of tyrosines in a biologically relevant context. However, selective tyrosine residues may be uniquely important for early signals supporting erythroid development.

Animals↗
PubMed1998

Utility of C57BL/6J x 129/SvJae embryonic stem cells for generating chromosomal deletions: tolerance to gamma radiation and microsatellite polymorphism.

We have previously reported a method for making nested deletion complexes in mice by irradiation of ES cells. The key to this technology is that F1 hybrid ES cells (called v17.2) of the genotype (BALB/cTa x 129/SvJae) retain germline colonizing ability after exposure to levels of ionizing radiation that induce chromosomal deletions. In an effort to identify other genotypes of ES cells that are suitable for this technology, the radiation sensitivity of the cell line v6.4, which is of the genotype (C57BL/6J x 129/SvJae), was investigated. After treatment with a range of radiation exposures, the developmental potential of these cells was assayed by injecting them into blastocysts to generate chimeric mice. These experiments showed that while cell lethality increased as the level of radiation increased, the surviving ES cells retained full totipotency at all exposure levels, up to 400 Rads. Because polymorphism between parental microsatellite alleles in the F1 hybrid ES cells is important for ascertaining the sizes of induced deletions, the 129/SvJ and 129/SvJae allele sizes of 48 microsatellite loci on chromosome (Chr) 17 were determined. This revealed a higher level of polymorphism between 129 and C57BL/6J on Chr 17. The radiation tolerance, high polymorphism between parental strains, and presence of the widely used C57BL/6J strain component make v6.4 ES cells an attractive cell line for generating radiation-induced chromosomal deletions.

Animals↗
PubMed1998

An antagonist peptide-EPO receptor complex suggests that receptor dimerization is not sufficient for activation.

Dimerization of the erythropoietin (EPO) receptor (EPOR), in the presence of either natural (EPO) or synthetic (EPO-mimetic peptides, EMPs) ligands is the principal extracellular event that leads to receptor activation. The crystal structure of the extracellular domain of EPOR bound to an inactive (antagonist) peptide at 2.7 A resolution has unexpectedly revealed that dimerization still occurs, but the orientation between receptor molecules is altered relative to active (agonist) peptide complexes. Comparison of the biological properties of agonist and antagonist EMPs with EPO suggests that the extracellular domain orientation is tightly coupled to the cytoplasmic signaling events and, hence, provides valuable new insights into the design of synthetic ligands for EPOR and other cytokine receptors.

Amino Acid Sequence↗
PubMed1998

Assignment of three Chinese xeroderma pigmentosum patients to complementation group C and one to group E.

Four Chinese patients with xeroderma pigmentosum (XP), who had different degrees of skin symptoms, were tested for their genetic complementation groups. Skin fibroblasts obtained from the patients were used for complementation analysis done by a cell-fusion technique. Three of the patients belonged to group C and one, who had the mildest cutaneous manifestations, to group E. This is the first report of a group E XP patient in China. Our present findings together with previous reports suggest that group C XP is more common in China, similar to the distribution among Caucasian XP patients but markedly different from the Japanese distribution.

Adolescent↗
PubMed1998

Deletion mapping of the head tilt (het) gene in mice: a vestibular mutation causing specific absence of otoliths.

Head tilt (het) is a recessive mutation in mice causing vestibular dysfunction. Homozygotes display abnormal responses to position change and linear acceleration and cannot swim. However, they are not deaf. het was mapped to the proximal region of mouse chromosome 17, near the T locus. Here we report anatomical characterization of het mutants and high resolution mapping using a set of chromosome deletions. The defect in het mutants is limited to the utricle and saccule of the inner ear, which completely lack otoliths. The unique specificity of the het mutation provides an opportunity to better understand the development of the vestibular system. Complementation analyses with a collection of embryonic stem (ES)- and germ cell-induced deletions localized het to an interval near the centromere of chromosome 17 that was indivisible by recombination mapping. This approach demonstrates the utility of chromosome deletions as reagents for mapping and characterizing mutations, particularly in situations where recombinational mapping is inadequate.

Animals↗
PubMed1998

Sensitization of acnu killing effects on HeLa S3 cells by MGMT antisense RNA transfection.

O6-methylguanine-DNA-methyltransferase (MGMT) plays a very important role in the cellular resistance to nitrosoureas drugs. Inhibition of MGMT might be a useful approach in tumor chemotherapy. In this study, the depletion of MGMT activity by retroviral-mediated antisense RNA transfection were reported. Three retroviral vectors expressing MGMT antisense RNA were constructed and transfected into HeLa S3 cells. The difference of MGMT mRNA, MGMT activity as well as cellular resistance to ACNU before and after transfection were observed. It was found that antisense RNA targeting 5' region and whole length of MGMT mRNA could partially deplete MGMT activity and enhance killing effects of ACNU. However, 3' region antisense RNA had no effect on MGMT modulation.

Antineoplastic Agents↗
PubMed1998

[Determination and significance of catecholamines in aqueous humor, plasma and 24 hour urine of patients with acute angle-closure glaucoma].

OBJECTIVE: To study the functional state of ocular and systemic sympathetic nervous system and the effects of its related neurohumoral factor, catecholamines (CA), on intraocular pressure (IOP) in patients with acute angle-closure glaucoma (AACG). METHODS: The levels of CA in the aqueous humor, plasma and the total amount of CA in 24 hour urine of cases with AACG during attack stage were determined with fluorometry, and the results were compared to that of patients with senile cataract and normal adults. RESULTS: The CA levels within aqueous humor and plasma and in 24 hour urine of the patients with AACG during attack stage were elevated obviously as compared with that of the control subjects (P < 0.001), and positively correlated with the level of IOP. CONCLUSION: During attack stage of AACG, the ocular sympathetic nervous system is highly excited and a large amount of CA is released into the aqueous humor, in the meantime the systemic sympathetic nervous system is also excited and CA is released into the blood circulation, which may play a certain role in the regulation of IOP. Possibly, CA is an important supplemental factor within the attack stage of AACG.

Acute Disease↗
PubMed1997

Membrane currents underlying the modified electrical activity of guinea-pig ventricular myocytes exposed to hyperosmotic solution.

1. Guinea-pig ventricular myocytes were superfused with hyperosmotic (sucrose) Tyrode solution (1.2-2.8 times (T) normal osmolality) for up to 40 min. Action potentials were recorded with microelectrodes, and membrane currents with the perforated- or ruptured-patch technique. 2. Hyperosmotic treatment for 20 min shrunk cell volume and hyperpolarized the membrane. Moderate (1.2-1.5 T) treatment caused biphasic changes in action potential configuration (rapid minor shortening quickly followed by lengthening to a stable 110% control duration). Severe (2.2-2.8 T) treatment caused triphasic changes (marked early shortening, strong rebound lengthening and subsequent pronounced shortening). At peak lengthening (6-10 min) action potentials (165% control duration) had a hump near -30 mV and slowed terminal repolarization. 3. In accordance with previous studies, hyperosmotic solution inhibited the delayed rectifier K+ current, and enhanced the outward Na(+)-Ca2+ exchange current (INaCa) at plateau potentials. A novel finding was that hyperosmolality reduced the amplitude of L-type Ca2+ current (ICa,L) and slowed its rate of inactivation. Experiments on myocytes loaded with indo-1 suggest that the reduction in ICa,L is due to a rapid elevation of [Ca2+]i. 4. When impaled myocytes were preloaded with EGTA, severe hyperosmotic treatment induced a rapid monotonic shortening of the action potential to a stable 20% of control duration. Addition of external K+ quickly nulled the hyperpolarization and slowly lengthened the action potential. 5. The results suggest that modified electrical activity in osmotically shrunken myocytes is primarily caused by increases in [K+]i, [Na+]i and [Ca2+]i: (i) elevated [K+]i hyperpolarizes the membrane (which may contribute to increased [Na+]i); (ii) elevated [Na+.]i shortens all phases of the action potential (increased outward-directed INaCa); and (iii) elevated [Ca2+]i has antagonistic plateau shortening (inhibition of inward ICa,L) and plateau lengthening (reduced outward INaCa) influences, as well as a strong subplateau lengthening effect (enhanced inward INaCa).

Action Potentials↗
PubMed1997

A Kaposi's sarcoma-associated herpesvirus-encoded cytokine homolog (vIL-6) activates signaling through the shared gp130 receptor subunit.

The present studies analyzed the biologic activity of a gene product (vIL-6) encoded by the recently discovered Kaposi's sarcoma-associated herpesvirus (KSHV) bearing 24.8% amino acid identity with human interleukin-6 (huIL-6). Based on this similarity, we hypothesized that this viral homolog might trigger the JAK/STAT pathway, which typically is engaged by IL-6 and other cytokines. Activation of receptor-associated Janus tyrosine kinases (JAKs) results in the subsequent phosphorylation of signal transducers and activators of transcription (STATs) leading to nuclear entry and transcriptional regulation of target genes. Treatment of HepG2 cells with culture medium containing recombinant KSHV-encoded vIL-6 led to rapid induction of JAK1 phosphorylation and a nuclear DNA-binding activity found to contain STAT1 and STAT3. An antibody to the IL-6 receptor (IL-6R) alpha subunit effectively neutralized the response to huIL-6 but failed to block STAT activation by vIL-6. In contrast, an antibody reactive with the gp130 subunit of IL-6R abrogated signaling of both responses. Moreover, a transfected cell line expressing human gp130 without IL-6Ralpha exhibited a robust response to vIL-6 but not to huIL-6. These results demonstrate that KSHV encodes a cytokine that activates specific JAK/STAT signaling via interactions with the gp130 signal transducing subunit independently of the IL-6Ralpha chain. This activity may have an impact on gp130-mediated signaling in response to native cytokines and thereby influence disease pathogenesis upon KSHV infection.

Antigens, CD↗
PubMed1997

Generation of radiation-induced deletion complexes in the mouse genome using embryonic stem cells.

As the genetic and physical mapping stage of the Human Genome Project nears completion, the focus is shifting toward the development of technologies for high-throughput analysis of gene function. Whereas DNA sequencing will enable the assignment of presumed function to a large number of genes in mice and humans, it is clear that the great majority of genes will have to be evaluated in vivo to accurately assess their role in a complex organism. While gene targeting in mouse embryonic stem (ES) cells is the current method of choice for the characterization of gene function in mice, it remains relatively labor intensive and lacks the throughput required for analysis of genome function on a large scale. Alternative methods of efficient mutagenesis will clearly be required for this task. Chromosomal deletions are powerful tools in the genetic analysis of complex genomes, enabling the systematic identification and localization of functional units along defined chromosomal regions. Not only are deletions useful for the identification of genetic functions, but they serve as mapping reagents for existing mutations or traits. While their use has been an essential tool in Drosophila genetics, classical mutagenesis in mice has been logistically impractical for generating deletions. We have previously described an efficient method for generating radiation-induced deletion complexes at defined regions in the genome using ES cells. In this article, we detail the methodological aspects of this technology and describe the applications of chromosomal deletions for characterizing gene function in ways that make optimal use of the information generated by the first stage of the Genome Project.

Animals↗
PubMed1997

Modulation of L-type Ca2+ current by fast and slow Ca2+ buffering in guinea pig ventricular cardiomyocytes.

Free Ca2+ near Ca2+ channel pores is expected to be lower in cardiomyocytes dialyzed with bis-(o-amino-phenoxy)-ethane-N,N,N',N'-tetraacetic acid (BAPTA) than with ethyleneglycol-bis-(beta-aminoethyl)-N,N,N',N'-tetraacetic acid (EGTA) because BAPTA chelates incoming Ca2+ more rapidly. The consequences of intracellular Ca2+ buffering by BAPTA (0.2-60 mM) and by EGTA (0.2-67 mM) on whole-cell L-type Ca2+ current (ICa,L) were investigated in voltage-clamped guinea pig ventricular cardiomyocytes; bulk cytoplasmic free Ca2+ (Cac2+) was monitored using the fluorescent Ca2+ indicator indo-1. ICa,L was augmented by approximately 12-fold when BAPTA in the cell dialysate was increased from 0.2 to 50 mM (half-maximal stimulation at 31 mM), whereas elevating internal EGTA from 0.2 to 67 mM increased ICa,L only by approximately 2-fold. Cac2+ was < 20 nM with internal BAPTA or EGTA > or = 20 mM. While EGTA up to 67 mM had only an insignificant inhibitory effect on the stimulation of ICa,L by 3 microM forskolin, ICa,L in 50 mM BAPTA-dialyzed myocytes was insensitive to forskolin-induced elevation of adenosine 3',5'-cyclic monophosphate (cAMP); conversely, ICa,L in cAMP-loaded cells was unresponsive to BAPTA dialysis. Cell dialysis with BAPTA, but not with EGTA, accelerated the slow component of ICa,L inactivation (tau S) without affecting its fast component (tau F), resembling the effects of cAMP-dependent phosphorylation. BAPTA-stimulated ICa,L was inhibited by acetylcholine and by the cAMP-dependent protein kinase (PKA) blocker H-89. These results suggest that BAPTA-induced lowering of peri-channel Ca2+ stimulates cAMP synthesis and channel phosphorylation by disinhibiting Ca(2+)-sensitive adenylyl cyclase.

Animals↗
PubMed1997

Chromosomal deletion complexes in mice by radiation of embryonic stem cells.

Chromosomal deletions ("deficiencies') are powerful tools in the genetic analysis of complex genomes. They have been exploited extensively in Drosophila melanogaster, an organism in which deficiencies can be efficiently induced and selected. Spontaneous deletions in humans have facilitated the dissection of phenotypes in contiguous gene syndromes and led to the positional cloning of critical genes. In mice, deletion complexes created by whole animal irradiation experiments have enabled a systematic characterization of functional units along defined chromosomal regions. However, classical mutagenesis in mice is logistically impractical for generating deletion sets on a genome-wide scale. Here, we report a high-throughput method for generating radiation-induced deletion complexes at defined regions in the genome using ES cells. Dozens of deletions of up to several centiMorgans, encompassing a specific locus, can be created in a single experiment and transmitted through the germline. The ability to rapidly create deletion complexes along chromosomes will facilitate systematic functional analyses of the mammalian genome.

Animals↗