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Z Chen

Publications and source records attributed to Z Chen.

At least 1,549 records · Page 86Linked to original sources
PubMed1989

Human 6-phosphofructo-1-kinase gene has an additional intron upstream of start codon.

A 6-phosphofructo-1-kinase-coding gene (pfk) has been purified from a human genomic library cloned in the lambda EMBL4 phage vector. This clone contains the nontranslated 5' flanking region of the human muscle pfk gene. Comparison of the nucleotide sequence determined by us with that of the human muscle pfk cDNA [Nakajima et al., FEBS Lett. 223 (1987) 113-116] indicates the presence of an additional intron extending from nucleotide (nt) -97 to -9 upstream of the ATG start codon. Furthermore, the human muscle pfk gene is more AT-rich than the rabbit gene. The available sequence of the two cDNAs shows 256 nt differences. Surprisingly, 71% of these sites are A's and T's in the human cDNA and C's and G's in the rabbit gene.

Animals↗
PubMed1989

Dehydrodolichyl diphosphate synthase in Sertoli and spermatogenic cells of prepuberal rats.

The specific activity of 2,3-dehydrodolichyl diphosphate synthase in homogenates of protease-treated seminiferous tubules, enriched spermatogenic cells, and Sertoli cells changed as a function of the age of prepuberal rats. The highest enzymatic activity occurred in each case in 23-day-old rats. Homogenates of pachytene spermatocytes, spermatids, or Sertoli cells had higher synthase activity than a whole testicular homogenate prepared by protease treatment of tubules. Enzymatic activity in pachytene spermatocytes expressed per mg of protein was about 1.7-fold higher than in spermatids, 5.3-fold higher than in spermatogonia, and about 8.3-fold higher than in spermatozoa. Therefore, the increase in spermatogenic cell synthase before day 23 can be accounted for by the appearance of the pachytene spermatocytes. Enzymatic activity decreased remarkably after the differentiation of spermatids into spermatozoa. Synthase activity in enriched Sertoli cell preparations was 1.5-2.3-fold higher than in spermatogenic cell preparations between days 15 and 30. Therefore, both spermatogenic cells and Sertoli cells contribute to changes in the enzymatic activity in seminiferous tubules during development. These changes may be important in regulating the availability of dolichyl phosphate for glycoprotein synthesis during early stages of differentiation.

Age Factors↗
PubMed1989

Relationship between vapor exposure and urinary metabolite excretion among workers exposed to trichloroethylene.

The exposure-excretion relationship was investigated in 140 trichloroethylene (TRI)-exposed workers and 114 nonexposed controls. The time-weighted average intensity of exposure to TRI during the shift as measured by the diffusive sampling method was compared with metabolite levels in the urine collected at the end of the shift in the second half of a working week, when the urinary metabolite levels are expected to reach a maximum. The TRI levels in breathing zone air of the exposed workers were mostly below 50 ppm. The urinary metabolite levels (i.e., total trichloro-compounds, trichloroethanol, and trichloroacetic acid) increased as a linear function of the TRI exposure. The relationship between the two exposure indicators was statistically significant in men, women, and both combined. The cross-sectional balance study at the end of the shift revealed that about 4% of TRI absorbed will be excreted at the end of the shift, in agreement with the long biological half-life of this chlorinated hydrocarbon solvent. A possible ethnic difference in the metabolism of TRI is discussed.

China↗
PubMed1989

Rearranging sequence located in the intron of the human T cell receptor gamma chain gene constant region.

Human T cell rearranging gamma genes encode membrane proteins which are expressed by a minor subset of T cells. Extensive studies have shown that TcR gamma gene rearrangements result from V gamma-J gamma recombinations. Here we analyze an unusual rearrangement involving a non-translatable sequence flanked by heptamer and nonamer signals in a Ti alpha/beta-positive T cell clone (JF1). This sequence, designated here as I gamma RS, is distinct from V, D or J elements. It is located in the first intron of the first constant region (C gamma 1) and homologous sequences are conserved in C gamma 2 introns. In JF1 cells the I gamma RS is juxtaposed to the J gamma 2 segment downstream to a V gamma 10-J gamma 1 rearrangement. The use of a cryptic splicing site induced JF1 cells to produce an aberrant large-sized transcript containing the I gamma RS 3' to the first exon of C gamma 1. Such a rearrangement occurring downstream to an inframe V gamma-J gamma junction may induce premature arrest of translation and lack of the C-terminal part of C gamma involved in gamma-protein assembly.

Base Sequence↗
PubMed1989

Reactivity of a new Pan-B monoclonal antibody (MA6) against human leukaemias.

The reactivity of a new Pan-B monoclonal antibody, MA6, against 69 cases of ALL, three plasmacytoma, 10 AML and five CML was evaluated. The antibody reacted positively against five of the 11 cases of U-ALL, 15 of the 26 C-ALL and all the cases of Pre B-ALL (one), B-ALL (one), B-CLL (12) and HCL (two). The MA6 did not react against the 16 cases of T-ALL, three plasmacytoma, 10 AML and five CML. The antibody has a broader spectrum of B-cell reactivity than CD9 and CD20 but is similar to the Pan-B antibody, CD19. MA6 appears to react against some of the very immature B cells and is therefore potentially useful, in conjunction with other antibodies such as CD9 and CD19, to confirm the B-lineage of some cases of U-ALL. The difference in the spectrum of reactivity against B-cell malignancies between MA6 and the other CDw40 antibody, G28-5, confirms their difference in antigenic specificity.

Antibodies, Monoclonal↗
PubMed1989

Effects of inhibition of thyroid function and of cold on melatonin synthesis and porphyrin content in the Harderian glands of male Syrian hamsters, Mesocricetus auratus.

1. Indole metabolism and porphyrin content of the Harderian glands of the male Syrian hamster were measured as functions of drug-induced hypothyroidism and exposure to cold conditions. 2. Harderian gland N-acetyltransferase (NAT) activity was reduced from control levels by hypothyroidism induced by methimazole; exposure to cold had no effect on NAT activity. 3. Immunoreactive melatonin in the Harderian glands was unaffected by the state of thyroid secretion. However, immunoreactive melatonin content declined after 180 and 270 min, at 4 degrees C, suggesting that Harderian gland melatonin may be involved in thermoregulation. 4. Porphyrin content of the Harderian glands was not affected by either thyroid secretion or cold.

Animals↗
PubMed1989

Dual bidirectional promoters at the mouse dhfr locus: cloning and characterization of two mRNA classes of the divergently transcribed Rep-1 gene.

The mouse dihydrofolate reductase gene (dhfr) is a housekeeping gene expressed under the control of a promoter region embedded in a CpG island--a region rich in unmethylated CpG dinucleotides. A divergent transcription unit exists immediately upstream of the dhfr gene which is coamplified with dhfr in some but not all methotrexate-resistant cell lines. We show that the promoter region for this gene pair consists of two bidirectional promoters, a major and minor promoter, which are situated within a 660-base-pair region upstream of the dhfr ATG translation initiation codon. The major promoter controls over 90% of dhfr transcription, while the minor promoter directs the transcription of the remaining dhfr mRNAs. The major promoter functions bidirectionally, transcribing a divergent 4.0-kilobase poly(A) mRNA (class A) in the direction opposite that of dhfr transcription. The predicted protein product of this mRNA is 105 kilodaltons. The minor promoter also functions bidirectionally, directing the transcription of at least two divergent RNAs (class B). These RNAs, present in quantities approximately 1/10 to 1/50 that of the class A mRNAs, are 4.4- and 1.6-kilobase poly(A) mRNAs. cDNAs representing both class A and class B mRNAs have been cloned from a mouse fibroblast cell line which has amplified the dhfr locus (3T3R500). DNA sequence analysis of these cDNAs reveals that the class A and class B mRNAs share, for the most part, the same exons. On the basis of S1 nuclease protection analysis of RNA preparations from several mouse tissues, both dhfr and divergent genes showed similar levels of expression but did show some specificity in start site utilization. Computer homology searches have revealed sequence similarity of the divergent transcripts with bacterial genes involved in DNA mismatch repair, and we therefore have named the divergently transcribed gene Rep-1.

Amino Acid Sequence↗
PubMed1989

Ph1+bcr- acute leukemias: implication of Alu sequences in a chromosomal translocation occurring in the new cluster region within the BCR gene.

Chromosomal breakpoints on chromosome 22 are located in the first intron of the bcr gene in half of the Philadelphia-positive acute leukemias (Ph1+bcr- AL). We have previously shown that, in these cases, the breakpoints are clustered in the 3' portion of the bcr gene first intron, particularly in a region called bcr2 or m-bcr-1. In order to search for mechanisms underlying the reciprocal chromosome translocation, molecular analysis of breakpoints on chromosome 9 and 22 were performed in a Ph1+bcr- acute lymphoblastic leukemia with bcr2 rearrangement. The comparison of rearranged sequences with their normal counterparts showed that human repetitive Alu sequences were physically linked to the translocation on both chromosomes. In addition an inverted Alu repeat was found 5' to each rearranged Alu sequence on chromosome 22 and 9, with an intervening sequence of 210 and 90bp respectively. This allows to propose a new model, still to be confirmed, of recombination after formation of two hairpin structures which could facilitate the genesis of the chromosomal accident.

Acute Disease↗
PubMed1989

Recognition and management of Budd-Chiari syndrome: report of one hundred cases.

Budd-Chiari syndrome is an unusual form of portal hypertension caused by occlusion of the hepatic venous outflow, and it is often confused with portal hypertension caused by liver cirrhosis. Its prognosis is poor, and optimal therapy remains to be established. This is a report of 100 confirmed cases of this syndrome treated from December 1982 to March 1988 at two vascular centers in China. Sixty-two male and 38 female patients, 15 to 62 years of age (mean age, 32.6 years) were treated. Seventy-six patients had intractable ascites, 56 had esophageal varices, and 22 had upper gastrointestinal bleeding. There were 37 cases of membranous obstruction, 57 cases of occlusion of the inferior vena cava above the confluence of the hepatic veins, and 6 cases of occlusion of the hepatic veins. Eighty-one patients were operated on. Operative mortality rate was 8.6% (7/81). Follow-up from 2 to 66 months revealed that 58 of the patients operated on (72%) had good results, whereas 11 of 19 (58%) patients treated nonoperatively died within 2 months after admission. On the basis of these data we conclude that the operative procedure must be tailored to the cause and underlying pathologic characteristics. Mesoatrial shunting is the operation of choice for patients with occlusion of the retrohepatic inferior vena cava and hepatic veins, and inferior vena cava--atrial shunting is the operation of choice for patients with occlusion of the inferior vena cava and patency of the hepatic veins. Membranotomy is used for patients with inferior vena cava webbing, and mesocaval shunting is used for patients with intrahepatic venous occlusion only.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Are most secondary acute lymphoblastic leukemias mixed acute leukemias?

A case of acute lymphoblastic leukemia (ALL) secondary to X-ray exposure is reported. The lymphoblasts expressed T-cell and myelomonocytic differentiation-related surface antigens. Clonal chromosomal abnormalities including t(2;12)(q25;q13),-10,der(10), del(11)(q14),der(12) and r were observed. A review of the cytogenetic data suggests that most secondary ALLs, with the exception of Burkitt type ALLs, may be biphenotypic or mixed acute leukemias.

Adult↗
PubMed1989

Ph1-positive, bcr-negative acute leukemias: clustering of breakpoints on chromosome 22 in the 3' end of the BCR gene first intron.

About 50% of the Philadelphia-positive acute leukemias undergo molecular rearrangements outside the now classical bcr sequence (or M-BCR-1) rearranged in chronic myeloid leukemia (CML). Most of the breakpoints on chromosome 22 have been shown to be clustered in a 10.8-kb region of the first intron of the BCR gene (called bcr2 or m-BCR-1). In this report we examined two cases of Ph1 acute lymphoblastic leukemia in adult patients that exhibited breakpoints in a 5-kb segment of the BCR gene first intron, 16 kb upstream of the previously described cluster, suggesting the possibility of a second minor breakpoint cluster. In addition, the breakpoints on chromosome 9 were located in a region just 5' of the c-abl exon la.

Chromosomes, Human, Pair 22↗