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S S Li

Publications and source records attributed to S S Li.

At least 91 records · Page 5Linked to original sources
PubMed1989

Structure of the human lactate dehydrogenase B gene.

Human genomic clones containing parts of the lactate dehydrogenase B (LDH-B) gene (approx. 25 kb in length) were isolated and characterized. The protein-coding sequence of human LDH-B gene is interrupted by six introns at codons nos. 42-43, 82, 140, 198, 237 and 278-279, and the positions of these introns are homologous to those of LDH-A genes from man and mouse. The 5' non-coding region of human LDH-B gene is interrupted by an intron six nucleotide residues upstream of the ATG translation-initiation site, whereas those of human and mouse LDH-A genes are interrupted at 24 nucleotide residues 5' to the ATG initiation codon. As is the case of LDH-A genes from man and mouse, there is no intron in the 3' non-coding region of human LDH-B gene.

Amino Acid Sequence↗
PubMed1989

Prostacyclin mediates splanchnic vascular response to norepinephrine in portal hypertension.

Portal hypertension is characterized by increased splanchnic blood flow. This hyperemia may be related to the documented in vitro impaired sympathetic response in portal hypertension. Because prostacyclin (PGI2) has been shown to be elevated in portal hypertensive rabbits, we studied whether PGI2 could mediate the reduced sympathetic response. We measured the change in the superior mesenteric artery resistance (Rsma) to norepinephrine infusion in chronic portal vein ligated (PHT) and normotensive rabbits, in both portal hypertensives and normals following cyclooxygenase blockade with 8 mg/kg indomethacin, and finally in portal hypertensive, cyclooxygenase-blocked rabbits with a constant IV infusion of PGI2 at 200 or 300 ng/kg/min. Dose-response curves were obtained and statistical comparisons were based on the dose of norepinephrine producing 50% of maximal Rsma response (ED50). Portal hypertensive rabbits had significantly higher ED50 (310 +/- 4.1 mg/kg) than normotensive rabbits (150 +/- 4.1 mg/kg, P less than 0.01). Cyclooxygenase blockade resulted in marked reduction of the ED50 in both groups and ablated the difference between normotensive and PHT rabbits (20 +/- 2.4 and 20 +/- 2.8 mg/kg/min, respectively). Prostacyclin infusion at 200 ng/kg/min increased the ED50 (80 +/- 2.5 mg/kg) and PGI2 infusion at 300 ng/kg/min increased the ED50 further (160 +/- 7.5 mg/kg/min, P less than 0.01 vs cyclooxygenase-blocked only rabbits). These results provide the first in vivo evidence of reduced splanchnic sensitivity to norepinephrine in portal hypertension and demonstrate that PGI2 will cause a dose-related decrease in sympathetic response.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

A method for hepatic arterial perfusion studies in the rat.

The current model for selective hepatic arterial infusion therapy was evaluated for its suitability for short-term pharmacokinetic experiments. This preparation consists of selective cannulation of the common hepatic artery via the gastroduodenal artery of the rat. Radioactive microspheres were injected to determine hepatic or extrahepatic sites of perfusion. Radioactive microsphere determination of hepatic arterial flow and cardiac output were also performed. Our data indicate that at high flow rates (2 ml/min), significant loss of drug would occur due to retrograde flow. Modification of the model to include temporary proximal hepatic artery occlusion ensures hepatic delivery of greater than 95% of drug. Furthermore, temporary hepatic artery occlusion does not alter cardiac output or hepatic arterial blood flow. Selective hepatic arterial infusion in rats with synchronous temporary hepatic artery occlusion is an adequate model for short-term pharmacokinetic studies.

Animals↗
PubMed1989

Estrogen-induced expression of mouse lactate dehydrogenase-A gene.

The synthesis of lactate dehydrogenase-A isoenzyme was shown to increase significantly in the uterus of immature mice treated by diethylstilbestrol. The expression of the mouse LDH-A promoter and cat fusion gene in Chinese hamster ovary cells was also induced by 17 beta-estradiol and diethylstilbestrol.

Animals↗
PubMed1989

Differential activity and synthesis of lactate dehydrogenase isozymes A (muscle), B (heart), and C (testis) in mouse spermatogenic cells.

Spermatogenic cells isolated from adult and prepubertal mice by unit gravity sedimentation were used to examine enzyme activities and synthesis of the lactate dehydrogenase (LDH) isozymes during spermatogenesis. The synthesis and activity of LDH-C4, the germ cell-specific isozyme, was detected earliest in isolated preleptotene and leptotene/zygotene spermatocytes prior to the mid-pachytene stage of meiosis reported previously. The LDH-C4 isozyme was prominent in pachytene spermatocytes, round spermatids, and condensing spermatids, whereas spermatozoa contained only the LDH-C4 isozyme. In addition, somatic-type LDH isozymes consisting primarily of LDH-B subunits were present in germ cells throughout spermatogenesis. This is in contrast to a previous report that the LDH-B subunit was not synthesized in germ cells. Sertoli cells were further shown to exhibit comparable amounts of five tetrameric LDH isozymes formed by combination of muscle-type LDH-A and heart-type LDH-B subunits.

Animals↗
PubMed1989

Gene expression during mammalian oogenesis and early embryogenesis: quantification of three messenger RNAs abundant in fully grown mouse oocytes.

Ribonuclease protection assays have been used to quantitatively assess changes in steady-state levels of specific mRNAs during oogenesis and early embryogenesis in mice. The mRNAs encode ZP3 (a glycoprotein that serves as a sperm receptor), LDH-B (heart-type lactate dehydrogenase), and MOM-1 (a protein of unknown function). MOM-1 and LDH-B are expressed in a variety of adult mouse tissues and midgestation embryos, whereas ZP3 expression is restricted completely to oocytes. All three mRNAs are expressed by growing mouse oocytes and accumulate to unusually high levels in fully grown oocytes as compared to somatic cells; 240,000, 200,000 and 74,000 copies mRNA per fully grown oocyte for ZP3, LDH-B and MOM-1, respectively. Steady-state levels of LDH-B and MOM-1 mRNA undergo a modest decline (approximately 20-40%) during ovulation when fully grown oocytes become unfertilized eggs and, in general, mirror the reported change in poly(A)+RNA levels during this period of development. On the other hand, the level of ZP3 mRNA declines dramatically (approximately 98%) during ovulation, from approximately 240,000 copies per oocyte to approximately 5000 copies per unfertilized egg, and ZP3 mRNA is undetectable in fertilized eggs (less than 1000 copies per fertilized egg). MOM-1 mRNA is expressed at relatively low levels in morulae (approximately 2000 copies per embryo) and blastocysts (approximately 5000 copies per embryo), whereas ZP3 mRNA remains undetectable (less than 1000 copies per embryo) at these stages of preimplantation development. These findings are discussed in the context of overall gene expression during oocyte growth, meiotic maturation and early embryogenesis in mice.

Animals↗
PubMed1988

Analysis of WAGR deletions and related translocations with gene-specific DNA probes, using FACS-selected cell hybrids.

We used the fluorescence-activated cell sorter (FACS) to select a series of somatic cell hybrids with deleted or translocated chromosome 11 segregated from its normal homolog. Analysis of these cell hybrids with gene-specific probes and for cell-surface marker expression has allowed us to order the markers and define a smallest region of overlap (SRO) for deletions associated with the WAGR (Wilms' tumor, aniridia, genitourinary abnormalities, and mental retardation) region of chromosome 11. Two translocation breakpoints in 11p13 (one associated with familial aniridia and one with a sporadic case of congenital renal dysfunction resulting from urethral and ureteral atresia) map within this SRO.

Animals↗
PubMed1988

Mapping of human lactate dehydrogenase-A, -B, and -C genes and their related sequences: the gene for LDHC is located with that for LDHA on chromosome 11.

Human testis-specific lactate dehydrogenase-C (LDHC) gene-related sequences are located with the LDHA gene on chromosome 11. The LDHB gene is on chromosome 12. Chromosomes 1, 2, 4, 9, and 10 appear to contain LDHA gene-related sequences, whereas the X chromosome and chromosome 13 possess LDHB gene-related sequences.

Blotting, Southern↗
PubMed1988

Cancer-associated lactate dehydrogenase is a tyrosylphosphorylated form of human LDH-A, skeletal muscle isoenzyme.

Cancer-associated lactate dehydrogenase is a tyrosylphosphorylated form of human skeletal muscle isoenzyme, since the partial amino acid sequences of human liver LDH-K/A protein were found to be identical with the known primary structure of human LDH-A isoenzyme and the LDH-A isoenzymes from human placenta and bovine muscle were shown to be tyrosylphosphorylated. This tyrosylphosphorylated LDH-K/A protein was also found to be complexed with 21 kD, 30 kD, and 56 kD proteins.

Amino Acid Sequence↗
PubMed1988

[Flow cytometry in analysis of precancerous lesions of the esophagus].

DNA content of the severe dysplasia cells in the esophageal epithelium was quantitatively analysed using flow cytometry and compared with those of the normal, mild dysplasia and cancer cells. The results showed that DNA index of the severe dysplasia cells was 1.27 +/- 0.11 and there was a significant difference between its value and those of the normal (1.0 +/- 0.02), mild dysplasia (1.01 +/- 0.03) and cancer cells (1.73 +/- 0.35). The DNA content of severe dysplasia cells lies between the normal and cancer cells. The hyperplasia degree of the severe dysplasia cells parallels their DNA contents. This study indicates that flow cytometry is a useful supplementary tool for diagnosis of the tumor.

DNA↗
PubMed1987

The cDNA and protein sequences of human lactate dehydrogenase B.

Human lactate dehydrogenase B (LDH-B) cDNA was isolated and sequenced. The LDH-B cDNA insert consists of the protein-coding sequence (999 bp), the 5' (54 bp) and 3' (203 bp) non-coding regions, and the poly(A) tail (50 bp). The predicted sequence of 333 amino acid residues was confirmed by amino acid composition and/or sequence analyses of a total of 185 (56%) residues from tryptic peptides of human LDH-B protein. The nucleotide and amino acid sequences of the human LDH-B coding region show 68% and 75% homologies respectively with those of the human LDH-A. The peptide map and amino acid composition data have been deposited as Supplementary Publication SUP 50139 (7 pages) at the British Library Lending Division, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies are available on prepayment [see Biochem. J. (1987) 241, 5].

Amino Acid Sequence↗
PubMed1987

Expression of the cDNA encoding for mouse sperm-specific lactate dehydrogenase C in Chinese-hamster ovary cells.

The cloned cDNA encoding for mouse sperm-specific lactate dehydrogenase C (LDH-C) was inserted immediately downstream to the MMTV 5' LTR promoter, and it was shown to synthesize mouse LDH-C polypeptide in Chinese-hamster ovary cells. The mouse LDH-C subunit and the endogenous Chinese-hamster LDH-A subunit formed in vivo a heterotetrameric LDH-A3C1 isoenzyme, and this novel isoenzyme exhibited enzymic activity utilizing lactate as substrate.

Animals↗
PubMed1987

Cyclic AMP-induced expression of the mouse lactate dehydrogenase-A promoter-cat fusion gene in Chinese hamster ovary wild-type cells, but not in cAMP-dependent protein kinase mutant cells.

The promoter region of mouse lactate dehydrogenase-A gene was fused with the chloramphenicol acetyltransferase gene of Escherichia coli, and the expression of this fusion gene was induced by cyclic AMP in Chinese hamster ovary wild-type cells, but not in mutants affecting the regulatory or catalytic subunit of cAMP-dependent protein kinase.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1987

Molecular cloning and nucleotide sequence of the cDNA for sperm-specific lactate dehydrogenase-C from mouse.

Mouse sperm-specific lactate dehydrogenase-C (LDH-C) cDNA was cloned and sequenced from lambda gt11 expression library. The LDH-C cDNA insert of 1236 bp consists of the protein-coding sequence (999 bp), the 5' (54 bp) and 3' (113 bp) non-coding regions, and the poly(A) tail (70 bp). The Northern blot analysis of poly(A)-containing RNAs from mouse testes and liver indicates that the LDH-C gene is expressed in testes but not in liver, and that its mRNA is approx. 1400 nucleotides in length. The nucleotide and amino acid sequences of the mouse LDH-C cDNA show 73% and 72% homologies, respectively, with those of the mouse LDH-A. The Southern blot analysis of genomic DNAs from mouse liver and human placenta indicates the presence of multiple LDH-C gene-related sequences.

Amino Acid Sequence↗
PubMed1987

Functional expression of the cDNA encoding for human lactate dehydrogenase-A in Chinese hamster ovary cells.

The cloned cDNA encoding for human lactate dehydrogenase-A was inserted immediately downstream to the SV40 early promoter, and it was shown to synthesize the human LDH-A polypeptide in Chinese hamster ovary cells. The human LDH-A subunit and the endogenous Chinese hamster LDH-a subunit formed in vivo a heterotetrameric LDH-a3A1 functional isoenzyme, indicating the conserved tertiary structure of both LDH-A subunits.

Animals↗
PubMed1987

Molecular nature of spontaneous mutations in mouse lactate dehydrogenase-A processed pseudogenes.

The presence of at least ten mouse LDH-A pseudogenes was demonstrated in the genomic blot analysis, and four different processed pseudogenes have thus far been isolated and characterized. In this report, the nucleotide sequences to two different mouse lactate dehydrogenase-A processed pseudogenes, M11 and M14, were determined and compared with the protein-coding sequences of the mouse and rat LDH-A functional genes. In the pseudogene M11, the sequence of 64 nucleotides from codon no. 257 to 278 was tandemly duplicated. In the pseudogene M14, the sequence of 22 nucleotides from codon no. 68 to 75 was replaced by an inserted repetitive sequence of 242 nucleotides homologous to a mouse truncated R element. The pattern of nucleotide substitutions accumulated in mouse LDH-A pseudogenes M11 and M14, as well as that of pseudogene M10 identified previously, was analyzed, and the substitution frequencies of the C or G at the CG dinucleotide were found to be high.

Animals↗