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C S Song

Publications and source records attributed to C S Song.

At least 19 recordsLinked to original sources
PubMed1992

Spatio-temporal expression of estrogen sulfotransferase within the hepatic lobule of male rats: implication of in situ estrogen inactivation in androgen action.

Estrogen sulfotransferase (EST) catalyzes transfer of the sulfate group from phosphoadenosine phosphosulfate to estrogenic steroids. Since estrogen sulfates do not bind to the estrogen receptor with high affinity, EST can control the intracellular level of the receptor-active estrogens. Androgen action in the rat liver, as indicated by the androgenic induction of alpha 2u-globulin, is inhibited by low levels of estrogens. Thus, in situ estrogen inactivation by EST is expected to increase hepatic androgen sensitivity. During the lifespan of the animal, rat liver undergoes three distinct phases of androgen sensitivity, i.e. prepubertal androgen insensitivity, androgen sensitivity after approximately 40 days of age, and androgen insensitivity during senescence (greater than 750 days). EST in the liver is expressed only after puberty, when the liver becomes androgen sensitive. Furthermore, localization of EST and its corresponding mRNA within the lobular unit of the liver demonstrates that only androgen-responsive hepatocytes located around the central vein contain immunoreactive EST and its corresponding mRNA. These temporal and spatial correlations of EST expression and hepatic androgen sensitivity support the concept that steroid-inactivating enzymes play important roles in sex hormone action.

Aging↗
PubMed1992

Estrogen sulfotransferase of the rat liver: complementary DNA cloning and age- and sex-specific regulation of messenger RNA.

Mammalian estrogen sulfotransferase (EST; EC 2.8.2.4) sulfurylates the hydroxyl group of estrogenic steroids by transferring the sulfate from a cosubstrate adenosine 3'-phosphate-5'-phosphosulfate. Sulfurylated steroids do not bind to the estrogen receptor with high affinity and, therefore, are hormonally inactive. We have purified rat liver EST and developed monoclonal antibody to this enzyme. By immunoscreening a lambda gt-11 expression library constructed from male rat liver cDNAs, the cDNA clone corresponding to EST was identified and isolated. A recombinant expression plasmid (pCMV5) containing this cDNA insert when transfected into COS-7 cells generated both immunologically and enzymatically active EST. With the help of this cDNA probe, we have explored the regulation of the EST mRNA in the liver and the possible role of this enzyme in sex hormone action. During the lifespan of male rats, only the young adult animals show hepatic androgen responsiveness. Also, estrogenic hormones strongly antagonize androgen action in the rat liver. Northern blot analysis of liver RNA derived from male rats of different ages shows that the androgen sensitivity of young adult animals is associated with a high expression of EST mRNA. During the same period, mRNA corresponding to dehydroepiandrosterone sulfotransferase is markedly (approximately 10-fold) down-regulated. Such a correlation is in concordance with the role of these enzymes in the maintenance of hepatic androgen sensitivity during young adult life by inactivating the estrogenic and sparing the androgenic steroids. Furthermore, the increase in the hepatic androgen sensitivity of androgen-treated female rats is also associated with the induction of EST.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1991

Androgen receptor messenger ribonucleic acid (mRNA) in the rat liver: changes in mRNA levels during maturation, aging, and calorie restriction.

By means of RNAase protection assay with an antisense cRNA probe, we have shown that the liver of the young adult male rat contains androgen receptor (AR) mRNA to a level of 4% compared to the prostate. Steady state levels of AR mRNA in the liver show both sex and age specificity. Compared to that of the male, the female liver contains a markedly reduced amount of AR mRNA. AR mRNA is almost undetectable in livers of prepubertal male (less than 35 days old) and senescent male (greater than 750 days old) rats. Both prepubertal and senescent animals are relatively insensitive to the androgenic induction of alpha 2u-globulin, a hepatic secretory protein. The age-dependent decline in hepatic androgen sensitivity and AR mRNA level can be delayed considerably by a 40% reduction in the dietary calorie intake. Analysis of poly(A)-containing RNA from two liver cell populations, hepatocytes and nonhepatocytes, revealed that only the hepatocytes that express alpha 2u-globulin gene contain AR mRNA. From these results and our earlier observation of in vitro induction of alpha 2u-globulin in isolated rat liver, we conclude 1) that androgen can act directly on hepatocytes to promote alpha 2u-globulin synthesis; 2) that changes in the hepatic androgen sensitivity during maturation and aging are reflections of the age-dependent expression of the receptor gene; and 3) that retardation of the age-dependent loss of androgen sensitivity by calorie restriction is due to a concomitant delay in the decline of the hepatic AR mRNA level.

Aging↗
PubMed1990

Structure and regulation of the senescence marker protein 2 gene promoter.

The liver-specific expression of the senescence marker protein 2 (SMP-2) in the male rat is markedly reduced during the androgen-sensitive state of young adulthood, whereas it is up-regulated during the androgen-insensitive phases of prepuberty and senescence. Nuclear runoff studies show that the age-dependent changes in SMP-2 expression are due to transcriptional regulation of the gene. In order to explore the mechanism of the regulatory process, we have cloned the upstream flanking regions of two distinct SMP-2 genes (SMP-2A and SMP-2B) and established their nucleotide sequence. These clones contain approximately 2.2 kb of the 5'-flanking sequence, exons 1 and 2, the first intron, and a portion of the second intron. The SMP-2 genes, as well as the upstream sequences, contain the sequence motifs for a number of cis-acting regulatory elements, such as the hepatocyte-specific element (HP1) and the androgen response element (ARE). S1 nuclease and primer extension analyses have established the transcription initiation sites for these genes. For functional analysis of the upstream sequences, we have constructed a hybrid plasmid containing the SMP-2A gene sequence (-1970 to +38 bases) fused to the structural gene for chloramphenicol acetyl-transferase (CAT). Upon transfection into rat hepatoma cells (FT02B), this construct was able to drive expression of the CAT gene. The same construct, however, failed to function in fibroblast-derived L cells, indicating tissue-specific regulation of the construct promoter.

Animals↗
PubMed1989

Loss of androgenic induction of alpha 2u-globulin gene family in the liver of NIH black rats.

Unlike all known strains of rat, the androgen-inducible alpha 2u-globulin gene family is totally silent in the liver of NIH black (NB) rats. No endocrinological or reproductive abnormalities are apparent, and the mRNA for the androgen-repressible hepatic protein SMP-2 is normally regulated in these animals. Furthermore, immunoblot analysis shows a normal level of the male-specific cytoplasmic androgen-binding protein. Cross-breeding of the NB male and Sprague-Dawley female shows that the hybrid male in the F-1 generation regains the androgen-dependent expression of alpha 2u-globulin in the liver. These results along with the observation of high constitutive level of alpha 2u-globulin mRNA in the preputial gland of NB rats indicate a tissue- and gene-specific regulatory defect which prevents androgenic induction of alpha 2u-globulin in the liver.

Alpha-Globulins↗
PubMed1988

Cloning, sequencing, and regulation of rat liver carnitine octanoyltransferase: transcriptional stimulation of the enzyme during peroxisome proliferation.

Several complementary DNAs for the peroxisomal enzyme carnitine octanoyltransferase (COT), cloned in the expression vector lambda gt11, have been isolated. Together, these clones cover 2143 bp of the COT cDNA sequence with an open reading frame for 523 amino acids. Northern analysis showed the mRNA size for this enzyme to be 3.5 kilobases. The 523 residue long amino acid sequence amounts to a molecular mass of 60,269 daltons, indicating that the cloned cDNAs contain most or all of the coding sequence for COT (Mr approximately 62,000). Hybridization studies showed that the increased COT activity in the liver of rats, fed the potent peroxisome-proliferating drug Wy-14,643, is associated with a more than 40-fold rise in the steady-state level of the COT mRNA.

Acyltransferases↗
PubMed1988

Pseudomonas aeruginosa cytotoxin stimulates secretion of amylase and protease zymogens with a concomitant decrease of mRNA levels in isolated rat pancreatic acini.

The action of Pseudomonas aeruginosa cytotoxin on isolated pancreatic acini was investigated. The release of amylase and serine protease zymogens from the isolated rat pancreatic acini was induced with increasing amounts of cytotoxin in vitro. The stimulated release of amylase reached 30% of total cellular content with 100 micrograms/mL of the purified cytotoxin. The induced release of amylase, trypsinogen, proelastase, and chymotrypsinogen reached the maximum after 75 minutes of incubation while lactate dehydrogenase began to appear after 15 minutes of incubation with a secondary biphasic increase at 75 min of incubation. The concentrations of acinar mRNAs of amylase, trypsinogen, proelastase, and chymotrypsinogen, as measured by dot-blot hybridization with the cloned cDNAs of amylase, trypsinogen I, proelastase II, and chymotrypsinogen B of the rat, decreased with time and were significantly lower than in the untreated acini. It is concluded that cytotoxin stimulates the release of amylase and protease zymogens with a concomitant increase in membrane permeability and a decrease of cellular mRNA levels. The inhibition of gene expression is attributable merely to a generalized toxic effect upon cellular metabolism.

Amylases↗
PubMed1988

Computed tomography of cavernous sinus diseases.

We retrospectively analyzed CT scans of 21 cavernous sinus lesions in an attempt to discover CT findings helpful to the differential diagnosis. With the integration of various CT observations it was possible to categorize the lesions into inflammatory, vascular, benign neoplastic and malignant metastatic lesions with few exceptions. Four of 5 cases of septic cavernous sinus thrombophlebitis revealed unilateral or bilateral multiple irregular filling defects in the enhancing cavernous sinus with or without orbital inflammatory change. Four of 5 cases of carotid-cavernous fistula demonstrated unilateral or bilateral diffuse bulging and homogeneous enhancement of the cavernous sinus with obliteration of normal low densities of cranial nerves and gasserian ganglion. Dilatation and tortuosity of superior ophthalmic vein were also associated. Four of 5 cases of benign neoplastic lesion showed well-circumscribed enhancing masses confined to the cavernous sinus with pressure erosion or hyperostosis of adjacent bone. Five of 6 cases of malignant metastatic lesion showed changes suggesting malignancy such as destruction of adjacent bone or associated manifestations of intracranial spread. As compared with the axial scan, coronal scans proved to be more sensitive in detection of subtle cavernous sinus expansion, and superior in evaluation of intracavernous neural structures, relationships with the pituitary gland and changes in the skull base. Axial scans, however, were superior in detection of associated orbital and intracranial abnormalities. Scans in both projections are needed in the evaluation of most cavernous sinus diseases.

Arteriovenous Fistula↗
PubMed1985

Antibodies to the alpha-subunit of insulin receptor from eggs of immunized hens.

Simple methods for the generation, purification, and assay of antibodies to the alpha-subunit of insulin receptor from eggs of immunized hens have been described. Chicken antibodies against the alpha-subunit inhibit insulin binding to the receptor and stimulate glucose oxidation as well as autophosphorylation of the beta-subunit. Thus the properties of chicken antibodies are very similar to those of antibodies found in human autoimmune diseases and different from rabbit antibodies obtained against the same antigen.

Adipose Tissue↗
PubMed1981

Reevaluation of properties of acetyl-CoA carboxylase from rat liver.

Rat liver acetyl-CoA carboxylase can be rapidly isolated by a new procedure which uses avidin-Sepharose affinity chromatography. The isolated enzyme has Mr = 260,000; none or very little of the proteolytic products of the carboxylase which are formed in conventional purification procedures are found in our preparations. It is apparent that the previously reported subunit of the carboxylase, with Mr = 230,000, is itself the product of proteolysis. The properties of the enzyme produced by our new method are quite different from those of the conventionally prepared enzyme. Our enzyme contains 6 mol of alkali-labile phosphate/mol of subunit, rather than 2 mol; the Km for acetyl-CoA is about 8-fold higher and the specific activity is only about one-fifth of that previously reported. The large amount of phosphate does not appear to cause the low specific activity of the new enzyme preparation, because alkaline phosphatase treatment reduces the number of phosphates/subunit from 6 to 3 mol but does not change the specific activity.

Acetyl-CoA Carboxylase↗
PubMed1981

Niacin Reduces Paraquat Toxicity in Rats.

Rats poisoned with paraquat benefited from daily niacin therapy. Niacin-treated rats showed delayed and reduced dyspnea. Deaths began approximately 30 hours later. The time required for niacin-treated rats to reach 50 percent mortality increased from 60 to 120 hours, and the dealth rate was reduced form 75 to 55 percent. The benefit by niacin is consistent with the demonstrated role of niacin in preventing cellular decreases of nicotinamide adenine dinucleotide during poisoning of bacteria by paraquat and by hyperbaric oxygen.

Animals↗
PubMed1981

Coenzyme A activation of acetyl-CoA carboxylase.

Acetyl-CoA carboxylase is activated by physiological concentrations of CoA. Activation of partially purified enzyme by CoA is accompanied by a decrease in the Km for acetyl-CoA from 0.2 mM to about 4 microM, which is the physiological concentration of acetyl-CoA in the cytosol. CoA activation of the purified enzyme is accompanied by an increase in the Vmax, without changing the Km for acetyl-CoA. The Km for acetyl-CoA of the purified enzyme is about 10 to 40 microM. The purification procedure results in a decrease in the Km for acetyl-CoA; under these conditions, CoA activation does not cause further lowering of the Km. CoA activation is accompanied by polymerization of the enzyme. However, CoA activation is not causally related to polymerization. There is one CoA binding site/subunit of acetyl-CoA carboxylase. CoA binding at that site is not affected by the presence of citrate, but palmityl-CoA inhibits CoA binding. CoA alone cannot reverse palmityl-CoA inhibition of the carboxylase. Bovine serum albumin and CoA together can activate the palmityl-CoA-inhibited enzyme. This indicates that the involvement of bovine serum albumin-like protein, CoA, and palmityl-CoA may play a physiologically significant role in the control of acetyl-CoA carboxylase.

Acetyl-CoA Carboxylase↗