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C Y Yu

Publications and source records attributed to C Y Yu.

At least 91 records · Page 5Linked to original sources
PubMed1990

[Effect of electroshock on learning-dependent long-term potentiation in rat hippocampal CA3 area].

Population spikes were recorded from hippocampal CA3 of freely moving rats following stimulation of the perforant path. Six rats were trained to perform conditioned drinking behavior. (1) Animals were treated with electroshock in less than 15 minutes after daily training session for a period of 6 consecutive days. Synaptic efficacy did not increase and the conditioned response could not be established during the behavioral training in four rats, synaptic efficacy was increased, the long-term potentiation (LTP) appeared and the conditioned behavior was established in other two rats. (2) After consolidation of conditioned behavior, electroshock temporarily caused suppression of the learning-dependent LTP and the correlative conditioned response. Both LTP and the correlative conditioned response recovered in one to four hours after electroshock. In these cases, the maximal development of LTP preceded the development of conditioned behavior. The results indicated that the learning-dependent LTP might be one of the neural substrates underlying learning and memory.

Animals↗
PubMed1989

A physical map linking the five CD1 human thymocyte differentiation antigen genes.

Human CD1 is a family of thymocyte differentiation antigens which consist of heavy chains with mol. wts between 43 and 49 kd binding to beta 2 microglobulin. They are distant relatives of the major histocompatibility complex (MHC) class I and II products. Five human CD1 genes have been described. Three (CD1A, -B and -C) code for the serologically defined CD1a, -b and -c antigens. The protein products of the other two genes, CD1D and CD1E, remain unknown. All CD1 genes are located on chromosome 1 and hence are independent of the MHC locus. In this paper, the tight linkage of the CD1 genes has been established by pulse field gel electrophoresis, cosmid cloning and walking techniques. The 190 kb of DNA linking all five CD1 genes has been spanned by 14 overlapping cosmids. The order of the genes in the CD1 complex is CD1D-CD1A-CD1C-CD1B-CD1E, and, with the exception of CD1B, they are arranged in the same transcriptional orientation. The genes are evenly spaced in the complex except for the distance between CD1D and CD1A, which is two to three times greater than the average.

Antigens, CD↗
PubMed1989

Unique sequence organization and erythroid cell-specific nuclear factor-binding of mammalian theta 1 globin promoters.

The theta 1 globin gene is an alpha globin-like gene, and started to diverge from the other members of the alpha globin family 260 million years ago. DNA sequencing and transcriptional analysis indicated that it is functional in erythroid cells of the higher primates, but not in prosimians and rabbit. The theta 1 promoter region of higher primates including man consists of GC-rich sequences characteristic of housekeeping gene promoters, and CCAAT and TATA boxes located further upstream. It is shown here that the housekeeping gene promoter-like region of human theta 1 contains two tandemly arranged, GC-rich motifs (GC-I and GC-II). Of these, GC-II interacts with nuclear factor(s) present in the globin-expressing, erythroleukemia cell line K562, before and after hemin induction. GC-I, however, interacts with nuclear factor(s) only present in hemin-induced K562 cells. These factors are different from previously reported erythroid cell-specific factors, and are not detectable in non-erythroid Hela cells. Furthermore, the sequence of the motif GC-I and its location relative to ATG codon have been conserved among all known mammalian theta 1 globin genes. Finally, and most interestingly, the CCAAT box of theta 1 is contained within a 38 bp internal segment of Alu repeat sequence. Immediately upstream from this CCAAT box-containing Alu repeat segment is a 241 bp Alu repeat pointing in the opposite direction. The conservation of this novel arrangement among the higher primates suggests that an inserted Alu family repeat and its flanking genomic sequence have co-evolved, for at least 30 million years, to provide the canonical CCAAT and TATA promoter elements of the theta 1 globin genes in higher primates.

Animals↗
PubMed1989

The rabbit CD1 and the evolutionary conservation of the CD1 gene family.

A comparison of the genes encoding the CD1 leucocyte differentiation antigens in man and mouse shows important differences which prompted us to analyze the CD1 genes of the rabbit. We have found that the rabbit genome contains multiple CD1 loci. Upon cloning and sequencing, one of these loci was found to encode the known rabbit CD1-like antigen (R-Ta) and to be closely related to the human CD1b gene, which is absent in the mouse, while a second rabbit gene is closely related to both the human R3 and the mouse CD1 genes. The data reinforce the notion of the existence of two classes of CD1 genes, one of which is conserved in all species, while the other, albeit also evolutionarily old, has been deleted in mice as well as in other rodents.

Amino Acid Sequence↗
PubMed1988

MR imaging of cavernous sinus involvement by pituitary adenomas.

The ability of high-resolution MR imaging (1.5 T) to detect invasion of the cavernous sinuses by pituitary adenoma was determined through a retrospective review of 74 patients. These patients were divided into three groups: 25 normal subjects, 24 subjects with invasive pituitary adenomas, and 25 subjects with noninvasive pituitary adenomas. A fourth group of 30 patients, who subsequently underwent surgery for pituitary adenoma, was evaluated prospectively by MR for the presence or absence of cavernous sinus invasion. Several features were analyzed: (1) the detectability of the medial and lateral dural margins of the cavernous sinus (2) the size and variation in intensity of compartments within the cavernous sinus (3) the relationship of endocrine function to the surgical and MR appearance of the cavernous sinus and (4) carotid artery displacement or encasement by tumor. The normal cavernous sinuses were usually symmetric, but their sizes varied. The lateral dural margin of the cavernous sinus was always recognized on MR as a linear, discrete, low-intensity area. The medial dural margin (pituitary capsule) was seen on MR in only two of the 25 normal patients. In all 24 patients with cavernous sinus invasion involvement was unilateral and was most common with laterally positioned prolactin or adrenocorticotropic hormone secretory adenomas. Invasion of the cavernous sinus was suspected by MR in only two of the 13 invasive microadenomas and was questionable in three. In 10 of the 11 macroadenomas with surgically proved dural invasion, MR demonstrated an asymmetric increase in size and intensity of the superior and inferior cavernous sinus compartments. Noninvasive macroadenomas compressed and displaced the cavernous sinus bilaterally. The prospective MR evaluation of 30 patients undergoing surgery for pituitary tumor revealed a sensitivity for predicting cavernous sinus invasion of 55%, a specificity of 85.7%, a positive predictive value of 62.5%, and a negative predictive value of 81.8%. No feature permitted certain distinction between invasive and noninvasive microadenomas, as the medial dural wall of the cavernous sinus could not be reliably identified. The most specific sign of cavernous sinus invasion was carotid artery encasement.

Adenoma↗
PubMed1987

Reduction of common carotid resistance upon stimulation of an area dorsal to the facial nucleus of cats.

In chloralose-urethane-anesthetized cats, electrical stimulation and glutamate injection on a small reticular area just dorsal to the facial nucleus (DFA) elicited an ipsilateral reduction in the common carotid resistance (CCR-reduction) with no or minimal change in other cardiovascular parameters. CCR-reduction was mediated via facial and glossopharyngeal nerves, involving partially muscarinic and partially non-muscarinic mechanisms.

Animals↗
PubMed1987

Molecular characterization of the HLA-linked steroid 21-hydroxylase B gene from an individual with congenital adrenal hyperplasia.

21-Hydroxylase deficiency which causes congenital adrenal hyperplasia is one of the most common defects of adrenal steroidogenesis. There are two 21-hydroxylase genes in man, A and B, and these have been mapped to the HLA class III region. Only the 21-hydroxylase B gene is thought to be active. To understand the molecular basis of congenital adrenal hyperplasia in a patient with the salt-wasting form of the disease, we cloned and characterized his single 21-hydroxylase B gene. The nucleotide sequence of this gene and a 21-hydroxylase B gene from a normal individual have been determined. Comparison of the two sequences has revealed 11 nucleotide alterations, of which two are in the 5' flanking region, four are in introns, one is in the 3' untranslated region and four are in exons. Two of the differences in exons cause codon changes, with Ser-269 and Asn-494 in the normal 21-hydroxylase B gene being converted to Thr and Ser, respectively. These amino acid substitutions may give an insight into those residues necessary for 21-hydroxylase enzymatic activity. We have also confirmed that the 21-hydroxylase A gene is a pseudogene due to three deleterious mutations in the exons. In addition, comparison of the 21-hydroxylase B gene sequence with other published sequences indicates that this microsomal cytochrome P-450 may be polymorphic.

Adrenal Hyperplasia, Congenital↗
PubMed1987

Definitive RFLPs to distinguish between the human complement C4A/C4B isotypes and the major Rodgers/Chido determinants: application to the study of C4 null alleles.

Definitive restriction fragment length polymorphisms (RFLPs) representing the exact locations responsible for isotypicity between the human complement components C4A and C4B, and their generally associated major Rodgers (Rg1) and Chido (Ch1) antigenic determinants, have been designed. By means of C4d-specific genomic probe for Southern blot analysis, a C4A gene can be defined by the presence of the 276 bp and 191 bp N1a IV fragments, while a C4B gene can be defined by a single 467 bp N1aIV fragment. In addition, an Rg1-expressing C4 gene can be represented by a 565 bp EcoO 109 fragment, and a Ch1-expressing C4 gene by a 458 bp EcoO 109 fragment, under the same conditions. All these polymorphic restriction fragments can be unambiguously and conveniently detected. In combination with the Taq I polymorphic patterns specific for the C4 loci and for the neighboring 21-hydroxylase genes, the nature and structure of the tandem C4,21-hydroxylase gene complex can be elucidated. In this study, it is inferred that the null allele of the HLA haplotype B44 DR6 C4A3 C4BQO is not a C4B allele, but probably encodes another C4A 3 allotype at the second C4 locus.

Alleles↗
PubMed1986

Structural basis of the polymorphism of human complement components C4A and C4B: gene size, reactivity and antigenicity.

The human complement components C4A and C4B are highly homologous proteins, but they show markedly different, class-specific, chemical reactivities. They also differ serologically in that C4A generally expresses the Rodgers (Rg) blood group antigens while C4B generally expresses the Chido (Ch) blood group antigens. C4A 1 and C4B 5 are exceptional variants which possess their class-specific chemical reactivities, but express essentially the reversed antigenicities. The genes encoding the typical Rg-positive C4A 3a and Ch-positive C4B 3 allotypes and the interesting variants C4A 1 and C4B 5 have been cloned. Characterization of the cloned DNA has revealed that the genes encoding the A 3a, A 1 and B 3 allotypes are 22 kb long, but that encoding B 5 is only 16 kb long. Comparison of derived amino acid sequences of the polymorphic C4d fragment has shown that C4A and C4B can be defined by only four isotypic amino acid differences at position 1101-1106. Over this region C4A has the sequence PCPVLD while C4B has the sequence LSPVIH, and this presumably is the cause of their different chemical reactivities. Moreover, the probable locations of the two Rg and the six Ch antigenic determinants have been deduced. Our structural data on the C4A and C4B polymorphism pattern suggests a gene conversion-like mechanism is operating in mixing the generally discrete serological phenotypes between C4A and C4B.

Amino Acid Sequence↗
PubMed1986

Molecular genetics of the fourth component of human complement.

The fourth component of human complement is encoded by two separate, but closely linked, loci, C4A and C4B, that have been positioned within the class III region of the HLA complex. While the two isotypes vary by only six amino acid residues, they differ significantly in haemolytic activity. Both loci are considerably polymorphic and this may be biologically relevant to ensure interaction with a wide range of pathogens. The number of C4 genes expressed is polymorphic as null alleles, total deficiency and duplication has been shown based on protein studies. Southern analysis of 24 different haplotypes with either C4A or C4B null alleles using the C4 probes showed that three of the null alleles were due to deleted genes but the majority appeared normal. A cosmid library was prepared from DNA of one of the deleted haplotypes and the region of deletion analysed by restriction mapping.

Alleles↗
PubMed1986

Improved methods of direct and cultured chromosome preparations from chorionic villous samples.

A new method is described for preparing direct mitotic chromosome spreads from chorionic villous samples, which has resulted in sufficiently high yields of well-banded metaphases to permit a complete standard chromosomal diagnosis in 20 of 20 cases. A method of establishing monolayer cultures from this material that can be harvested from 3 to 7 days after initiation is also presented.

Cells, Cultured↗
PubMed1985

Polymorphism of human complement component C4.

An assessment has been made of the polymorphism of human complement component C4 by comparing derived amino acid sequences of cDNA and genomic DNA with limited amino acid sequences. In all, one complete and six partial sequences have been obtained from material from three individuals and include two C4A and two C4B alleles. Differences were found between the 4 alleles from 2 loci in only 15 of the 1722 amino acid residues, and 12 lie within one section of 230 residues, which in 1 allele also contains a 3-residue deletion. In three variable positions, an allelic difference in one C4 type was common to the other types. Three nucleotide differences were found in four introns. In spite of marked differences in their chemical reactivity, the many allelic forms appear to differ in less than 1% of their amino acid residue positions. This unusual pattern of polymorphism may be due to recent duplication of the C4 gene, or may have arisen by selection as a result of the biological role of C4, which interacts in the complement sequence with nine other proteins necessitating conservation of much of the surface structure.

Amino Acid Sequence↗
PubMed1985

Expression of T4 early genes 62, 44, 45 and 46 in the lambda-T4 recombinant phage lambda 806-17.

A lambda-T4 recombinant phage, lambda 806-17, which carries the T4 early genes 62, 44, 45 and 46, was studied inside a homoimmune lysogen. Under such conditions, gene expression from the lambda promoters is represented. Results showed extensive expression of gene 46, and significant expression of genes 62 and 45. The expression of these early T4 genes is presumed to depend on T4 promoters included in the cloned fragment. A new promoter proximal to gene 46 is implicated. The results also indicate that the extent of gene expression, in terms of complementation, increases with the time allowed for expression.

Escherichia coli↗